Adductor muscle and tendon injury

INTRODUCTION — Groin injuries are common in sport, particularly those involving rapid acceleration, deceleration, and change of direction. Often these injuries involve acute strains (minor tears) of the adductor muscles or chronic damage to the adductor tendons.

The clinical presentation, evaluation, and management of acute and chronic adductor muscle and tendon injuries are reviewed here. Other musculoskeletal injuries of the lower extremities are discussed separately. (See "Hamstring muscle and tendon injuries" and "Quadriceps muscle and tendon injuries".)

ANATOMY AND BIOMECHANICS — The adductors of the hip are part of the inner hip and thigh musculature and range from the lower pelvic bone to the femur and knee region (figure 1 and figure 2). They lie between the quadriceps muscles anteriorly and the hamstring muscles posteriorly. The adductors are innervated by the obturator nerve (figure 3), with the exception of the pectineus, which receives innervation from the femoral nerve. The hip adductors determine the shape of the medial thigh and include the following muscles:

●Adductor magnus muscle (figure 4) – One of the biggest muscles of the human body, the adductor magnus originates at the inferior pubic ramus, the ischial ramus, and the ischial tuberosity, and inserts both at the linea aspera ("muscular, fleshy insertion") and the medial femoral epicondyle ("tendinous insertion"). The superficial part of the adductor magnus is supplied by the tibial nerve.

●Adductor longus muscle (figure 5) – The adductor longus originates at the superior pubic ramus and the pubic symphysis and inserts at the linea aspera. Distally it forms an aponeurosis (vasto-adductor membrane) that extends to the vastus medialis muscle.

●Adductor brevis muscle (figure 6) – The adductor brevis originates at the inferior pubic ramus and inserts at the linea aspera.

●Adductor minimus muscle – The adductor minimus describes a proximal separation of the adductor magnus, and it is sometimes considered part of the adductor magnus, constituting its upper, lateral part. The muscle is found in approximately half the population and extends from the inferior pubic ramus to the linea aspera [1].

●Pectineus muscle (figure 7) – The pectineus travels from the superior pubic ramus to the pectineal line and linea aspera of the femur. It receives additional innervation from the femoral nerve.

●Gracilis muscle (figure 8) – The gracilis travels from the inferior border of the pubic symphysis to the superficial pes anserinus of the tibia. Its tendon is easy to palpate in the inguinal region, together with the tendon of the adductor longus muscle.

The adductors contain complex musculotendinous units with areas of muscle fiber, a musculotendinous interval, tendon, and insertional entheses constituting the bone-soft tissue interface. The adductor tendons orient in the direction of the forces applied by the adductor muscle on the femur.

As the name adductor suggests, one main function of the hip adductors is adduction of the hip joint. In addition, these muscles contribute to hip external rotation (pectineus, adductor brevis, and adductor magnus), hip internal rotation (tendinous insertion of the adductor magnus), hip flexion (all), and hip extension (tendinous insertion of the adductor magnus) [2]. These functions of the adductors are performed when the foot is not planted (ie, open chain movements).

In contrast, when the foot is planted (ie, closed chain movements), the adductor muscles play an important role in providing stability. During a single-leg stance or landing, the adductor complex helps to stabilize the pelvis, so it remains balanced and aligned with the torso and lower extremities and contributes to medial knee stability, preventing the knee from caving in towards the midline. The stability provided by the adductors is particularly important during activities performed on a single leg, such as kicking a ball and performing cutting maneuvers during sport.

The femoral artery and vein and the saphenous nerve travel within a groove between the adductor magnus and adductor longus and the vastus medialis muscles (figure 9). This so-called adductor canal (or Hunter's canal) is covered in part by the vasto-adductor membrane. Distally, it ends between the distal muscle and tendon insertion of the adductor magnus.

CLASSIFICATION — An adductor strain is defined as an injury to any part of the muscle-tendon unit that produces pain on palpation of the adductor muscles or tendons or their bony origin with or without pain during resisted adduction [3]. Adductor injuries may be classified according to anatomy and severity.

Site of injury — Anatomic classification refers to the muscle(s) involved (adductor longus, brevis, or magnus) and the location of injury, which is described as predominantly muscular, tendinous, musculotendinous, insertional (enthesis), or an avulsion injury (tendon or bone). The adductor longus is most commonly injured during sporting activity and is the most common site for insertional tendinopathy. The relative length, greater tendon to muscle ratio, and weaker pubic attachment may make the adductor longus more susceptible to injury [4].

The location and type of the injury is often age-dependent [5]. Common associations with particular injury types include the following:

●Muscular – Skeletally mature adults

●Myotendinous – Skeletally mature adults

●Tendinous – Older adults (over 35 years of age)

●Apophysis (bony avulsions) – Adolescents with open apophyses

●Tendon avulsions – Skeletally mature adults

Muscle and tendon injuries often occur in zones of transition (eg, regions where muscle and tendon fibers intertwine) because these are areas of potential weakness in the muscle-tendon-bone unit [5]. Adductor pain may also occur as part of a complex regional groin syndrome.

Grade of injury — Most texts classify muscle and tendon strains in the same manner; some injuries involve muscle and tendon (musculotendinous), so a uniform classification scheme is appropriate.

Muscle and tendon tears may be graded according to the severity of the injury, as described by various authors [6]:

●Grade 1 – Tear of a small number of muscle and/or tendon fibers that causes pain but no or minimal loss of strength or motion.

●Grade 2 – Tear of a significant number of muscle and/or tendon fibers causing pain, swelling, decreased motion, and decreased strength but not complete loss of function.

●Grade 3 – Complete disruption of the muscle-tendon unit with loss of function.

Chronicity of injury — Adductor injury may be described as acute or chronic. Acute tears (typically diagnosed no longer than six weeks from the time of injury) are characterized by tissue disruption and local bleeding. Chronic injuries are marked by microscopic anatomical fiber disruption and distortion, muscle scarring and fiber shortening, tendon thickening, and other types of degenerative change. (See "Overview of overuse (persistent) tendinopathy".)

EPIDEMIOLOGY AND RISK FACTORS — The exact incidence of adductor muscle and tendon injury in sport is difficult to determine because many players play through minor muscle strains, which are not reported to trainers or clinicians, and adductor injury may occur as one part of a more complex groin injury [4].

Although numbers vary by sport, adductor strains (muscle tears) are reported to comprise approximately 10 percent of athletic injuries overall, and a large percentage of groin injuries [7-13]. Sports that place greater demands on the adductor muscle group, in particular, more frequent eccentric contraction, appear to have a greater incidence of adductor injuries. These sports include soccer (football), futsal, ice hockey, and basketball. Adductor injuries comprise up to 43 percent of all muscle strains among ice hockey players [14,15], while groin injuries, including adductor strains, make up 10 to 18 percent of soccer-related injuries [4,8]. Among women soccer players, the incidence of adductor injury ranges from approximately 9 to 13 percent [16,17].

A number of risk factors are associated with adductor muscle and tendon injury.

Intrinsic factors associated with an increased risk of adductor injury include the following:

●Decreased adductor-to-abductor strength ratio (ie, abductors significantly stronger than adductors) [18,19].

●Decreased hip abduction or rotational mobility [13,17,19].

●Previous adductor injury [13,19-21].

●Leg length discrepancies: These may lead to abnormal gait and repetitive stress on the adductors [22].

●Dominant kicking leg, which has a higher incidence of adductor injury in soccer [23].

The effect of adductor inflexibility is controversial with some studies showing an association with increased injury risk and others showing no association [18,24].

Extrinsic factors associated with an increased risk of adductor injury include the following:

●Poor conditioning and lack of preseason preparation [20].

●Muscle fatigue.

Muscle fatigue predisposes to injury and may develop because of inadequate conditioning or due to the duration and intensity of a match [25].

●Inadequate warm-up.

Cold muscles are more disposed to strains. This may occur because the warm-up is inadequate or because the muscles cool off during a lull in the intensity of play, as might occur during a baseball game.

●Ice skating style and technique, particularly with increased velocity.

●Skating style technique for cross-country skiing [26].

Stride rate and stride length increase significantly as skating speed increases, whereas the overall motion of the hip, knee, and ankle do not increase. To achieve the increased stride rate needed for faster skating, the rate of hip abduction increases significantly, along with activation of the adductors. Biomechanical studies of skaters show that the adductor magnus muscle exhibits significantly larger increases in peak muscle activation and duration of activation with increased skating speed [27]. Fast skating thus involves substantial, repeated eccentric contractions of the adductor magnus, which likely increase the potential for adductor strain. Characteristics of the blades, including the pitch and level of the edges, the radius of the hollow and contour, as well as the quality of the ice surface, may affect the risk of adductor injury [28].

●Skiing format; giant slalom places greatest load on adductors [29].

According to a biomechanical study in which the muscle activity patterns of six alpine skiers were compared during nine runs each of wedge (W), short radius parallel (P), and giant slalom (GS) turns, the peak electromyelogram (EMG) amplitudes for the adductors, amongst other muscle groups, during the GS was greater than 150 percent of the maximal voluntary muscle contraction, suggesting that GS skiing places greater stress on the adductors than other maneuvers.

●Increasing age is associated with a greater risk of adductor injury and recurrence of injury [19].

●Medications.

A number of medications are associated with an increased risk of muscle and tendon injury. These include glucocorticoids, fluoroquinolone antibiotics, and statins. These issues are reviewed separately. (See "Major adverse effects of systemic glucocorticoids", section on 'Bone and muscle effects' and "Fluoroquinolones", section on 'Musculoskeletal' and "Statin muscle-related adverse events".)

●Anabolic steroid abuse.

Tendon rupture has been linked with anabolic steroid abuse on the basis of a small number of published case reports and experimental data from animal models suggesting that steroids alter the biomechanical properties of tendons [30]. (See "Use of androgens and other hormones by athletes".)

●Pregnancy-related adductor pain has been described, but there appears to be no evidence of increased adductor injury risk.

MECHANISM OF INJURY

Overview of injury types and related mechanisms — Adductor muscle and tendon strains (low and moderate – grade 1 and 2 – tears) and, less often, complete tears are sustained most often during sports that involve repeated sprints, including most field sports, and sports that require explosive lower extremity movements, such as karate, gymnastics, and high jumping [2,4,8]. An observational study using video analysis of adductor longus injuries sustained by male professional football (soccer) players categorized such injuries as open chain (involving kicking or jumping) or closed chain (involving rapid change of direction or reaching) [31]. These injuries were attributed to sudden, powerful muscle activation during rapid muscle lengthening.

Specific mechanisms involved in such adductor injuries include:

●Rapid adduction of the hip against an abduction force (eg, sudden change of direction in football [soccer], basketball, squash, tennis, or comparable sports).

●Acute forced abduction that places an exaggerated stretch on the tendon (eg, stretching for a return in tennis, sliding tackle in football (soccer) with legs apart (figure 10)).

●Sudden acceleration with sprinting, including rapid change of direction.

Sprinting (including skating sprints in hockey), rapidly changing direction (cutting), jumping to catch or head a ball, running uphill, and landing after a jump are all examples of actions that may cause an adductor muscle or tendon strain. During all the movements described here, considerable reaction forces act through the anterior pelvis, in particular the symphysis pubis, as well as the inguinofemoral aponeuroses and parasymphyseal muscles, which include the hip adductors and abdominals. Poor biomechanics that place added stress on the adductors may also contribute to such injury.

Other types of adductor injury are associated with particular mechanisms:

●Adductor muscle contusions result from a direct blow to the inner thigh from a ball, boot, opponent's knee, or other hard object.

●Adductor tendon avulsion is caused by an eccentric overload due to forced abduction of the hip during attempted contraction of the hip adductors [32]. Such movements might occur during skiing, rugby, or football.

●Chronic adductor strain (overuse injury) may be due to significant, repetitive forces exerted through the area of the adductors. These may be influenced by biomechanical factors, such as external rotation of the hip, genu valgus, or significant pronation during gait.

Tendon injury — Tendons consist of collagen fibrils and a supporting matrix oriented in the direction of the forces applied to the tendon during its interactions with the attached muscles and bone. During athletic activity, tendons, not muscles, move the most, shortening and lengthening like springs as they transmit and absorb forces. The normal tendon is elastic and reforms upon withdrawal of the applied force (assuming tendon motion remains within its physiologic range).

Acute severe adductor tendon tears are rare. They typically occur with forced hip abduction, as may occur during water skiing, gymnastics, and contact sports. The forced abduction may occur while the athlete is adducting their hip, as when two players contesting for a soccer ball strike the ball with their feet simultaneously. Alternatively, the abduction force may be exerted on the hip while the adductors are isometrically contracting to maintain stability, as during a single leg stance.

Chronic tendon injuries are more common. Disuse, overuse, injury to other parts of the lower limb kinetic chain, and increasing age all can alter tendon collagen and matrix structure and the tendon's line of action, and reduce tendon elasticity [5]. Alterations in tendon structure and function may not be evident clinically or radiologically but can begin a cycle leading to further injury as greater forces are required to produce the same degree of tendon deformation during movement. The pathophysiology of chronic overuse tendinopathy is discussed in detail separately. (See "Overview of overuse (persistent) tendinopathy".)

CLINICAL PRESENTATION

History — The patient should be asked to describe the onset of pain (acute or chronic), its severity, and any radiating features. It is important to ask about any trauma, including the mechanism of injury, and any factors that aggravate or alleviate pain. The common mechanisms associated with specific adductor injuries are described above. (See 'Mechanism of injury' above.)

Previous injury of the adductor muscles or other muscle groups around the pelvis may predispose to adductor injury and the clinician should inquire specifically about such a history. The patient's occupational status and recreational activities should be noted. Particularly if the pain is not associated with trauma, it is important to ask about constitutional symptoms (eg, fever, nausea, urinary symptoms), which, if present, suggest a medical condition rather than musculoskeletal injury. (See "Evaluation of the adult with abdominal pain" and "Causes of abdominal pain in adults" and "Evaluation of the adult with nontraumatic abdominal or flank pain in the emergency department".)

Presentation and examination findings of particular injuries — Typical features associated with specific adductor injuries include the following:

●Adductor muscle strains (grade 1 injury) – The athlete may recall the onset of injury or the onset may be insidious, and pain not noted until completion of the activity. There is no bruising; tenderness is present over the injured muscle but without a palpable defect. Pain is reproduced with resisted adduction, but there is minimal loss of power. (See 'Grade of injury' above.)

●Adductor muscle strains/tears (grade 2 or 3 injury) – The athlete usually recalls exactly when and how the injury was sustained, typically during a high-risk activity (eg, sprinting, sudden change of direction at speed, or exaggerated stretch during sport), and was forced to stop participating at the time of injury; gait is severely affected, and crutches are often required. Findings typically include bruising and tenderness over a palpable defect. Resisted hip adduction is almost always markedly compromised and painful; both hip adduction and straight leg raise are notably weaker than on the unaffected side.

●Adductor muscle contusion – Contusions result from a direct blow to the inner thigh from a ball, boot, opponent's knee, or other hard object. Typically, the athlete recalls the event and mechanism of injury. A hematoma may develop if blood vessels have been damaged; bruising usually manifests hours to days later. The area of contact is usually erythematous or bruised and tender. Depending on the extent of the injury, the athlete's function is affected to varying degrees. Gait is often antalgic. Adduction against resistance is painful and weaker on the affected side.

●Proximal tendon avulsion – Detachment of one or more of the adductor muscles from its origin at the pubic ramus causes immediate and sustained dysfunction. Athletes may recall a "pop" while sprinting or cutting or at the time of direct contact. Gait is severely restricted or impossible, requiring the use of crutches. Examination reveals proximal bruising, significant tenderness along the pubic ramus, a palpable defect proximally, and distal swelling over the retracted muscle. Hip adduction and straight leg raises against resistance are substantially weaker than the unaffected side.

●Distal tendon avulsion (rare) – The site of the distal insertion at the medial femoral epicondyle is tender. Proximal retraction of the tendon creates a palpable lump. Hip adduction and straight leg raises against resistance are substantially weaker than the unaffected side.

●Chronic tendinopathy (overuse injury) – Tendinopathy develops over weeks to months as a result of repetitive loading with inadequate recovery time. Rather than recalling a specific incident, the athlete may note a change in routine (eg, increased training volume) or increased performance of certain exercises, such as cutting or sprint drills. Athletes often complain of pain at the start of running-associated exercise and after cooling down. Higher-grade tendon injuries persist during running and are exacerbated by cutting, jumping, acceleration, and deceleration maneuvers. Both proximal and distal adductor tendons may be involved, and palpation of the affected portion of the tendon elicits pain. Resisted hip adduction reproduces pain to varying degrees depending upon the severity of the injury. Power may be diminished but not as significantly as with muscle tears.

Physical examination — Examination for adduction injuries often entails a wider assessment of potential associated hip and groin injuries. Important elements of the hip and groin assessment relevant to adductor injury are reviewed briefly here, but a detailed discussion is provided separately. Examination techniques specifically for assessing the adductors are described below. (See "Musculoskeletal examination of the hip and groin".)

Performance of the examination — To examine the groin properly, the patient should be in his or her underwear. Starting the examination with the patient standing allows the clinician to look for a change in thigh contour and areas of swelling or bruising. Ecchymosis is usually associated with higher-grade muscle tears or avulsions. Bruising may only manifest hours or days after the injury and may travel distally into the thigh or scrotum.

The clinician should observe the patient walking, if possible, looking in particular for the following:

●Trendelenburg gait, caused by weakness of the gluteus medius (figure 11 and picture 1).

●Coxalgic gait, in which the patient quickly unloads the painful leg (ie, limps).

After inspecting the area and observing the patient's gait, the clinician asks the patient to perform several actions that stress the adductor muscles and compares one side with the other. These movements include lunging, one-legged squat, adduction without and with resistance, hip flexion, and hip extension. With severe injuries, the patient may not be able to perform these maneuvers.

Next the patient lies supine and is asked to identify the precise location of pain (groin, pubis, iliac crest, greater trochanter, thigh, buttock, sacroiliac joint, abdomen, lumbar spine). The clinician carefully inspects and palpates the pertinent anatomic structures, noting whether palpation of any particular structure reproduces the patient's pain. Important structures to assess include:

●Adductor muscles. These should be palpated systematically, moving from the proximal origins distally to their insertions, and compared with those of the uninjured side. The focus is on identifying areas of focal tenderness, palpable defects (suggesting high-grade muscle or tendon tears), and retracted muscles (suggesting avulsion injury).

●Adductor longus origin at the pubic symphysis (picture 2).

●Inferior pubic ramus, with particular attention to the origins of the adductor magnus and brevis (figure 4 and figure 6).

When examining any region it is important to be systematic and to develop a routine that is easily reproduced. This helps clinicians avoid missing important parts of the examination, and makes comparisons easier. Below is the author's approach to the examination of the patient with a suspected adductor injury. For each test described, pain can be registered as "yes" or "no" and strength recorded as "weak," "intermediate," or "strong." The patient lies supine on an examination table for all the tests described below.

●Palpation of the symphysis joint (figure 12 and figure 2 and figure 13).

Locate the symphysis joint using gentle palpation with the index finger or index and middle finger together. Then, push the joint firmly in an anterior-posterior direction using a fingertip to elicit pain or instability.

●Palpation of the rectus abdominis muscle (figure 14).

Palpate the distal portion of the rectus abdominis muscles using two or three fingers. When the insertion at the pubic bone is located, move your fingertips proximally just a few millimeters and then press posteriorly to assess tenderness and then distally directly onto the pubic bone. Note any tenderness and compare this with the contralateral side. With high-grade tears, a defect may be palpated, especially in lean patients.

●Palpation of the psoas muscle (figure 15 and figure 16).

Place both hands on the same lateral portion of the lower abdomen at the level of the anterior superior iliac spine. Palpate gently using only the fingers (picture 3). Begin by locating the lateral edge of the rectus abdominis muscles, and palpate lateral to this border. Gently press the fingers posteriorly while pushing the abdominal structures away to reach the iliopsoas muscle. The patient must remain relaxed for effective palpation so be gentle and go slowly. When your hands are as deep as possible, ask the patient to elevate the foot on the side being tested about 10 cm, which causes the psoas to contract. Palpate the contracted psoas muscle over as large an area as possible without lifting the fingers from the skin. Pain with contraction of the muscle suggests injury, which may be localized to a specific area of the muscle by this palpation technique.

●Palpation of the adductor longus muscle insertion.

Place the lower extremity to be tested on a pillow with the hip flexed, abducted, and externally rotated, and the knee slightly flexed. During passive abduction of the hip, the adductor longus becomes prominent. The extremity being examined must remain relaxed. Tell the patient to note only pain and to ignore the natural sensitivity of the area. Using two or three fingers, palpate the length of the adductor longus tendon from the musculotendinous junction to its insertion at the pubic bone (picture 2). Use firm pressure to palpate the insertion area, including the bone (a radius of approximately 1 cm). The adductor longus attaches medially and superiorly, and the examiner should palpate its origin from the symphysis to the superior border of the ramus. The origin at the pubic tubercle can be palpated as a tight cord. Note any tenderness greater than that on the uninjured side, and any prominence (eg, hematoma) or defect (consistent with a tear) in the muscle or tendon.

●Passive stretching of the adductor muscles.

Passively abduct the lower extremity to be tested, holding it with one hand, while making sure the foot points straight up. With the other hand, the examiner braces the pelvis to stabilize the testing position. Gradually, increase abduction of the lower extremity until the adductor muscles are maximally stretched (picture 4).

●Adduction of the legs against resistance.

Stand at the end of the examination table with your hands and lower arms between the feet of the subject to hold them apart. Ask the patient to point both feet straight up and then press them together with maximal force against the resistance of your hands, without lifting either leg or the pelvis (picture 5).

Another useful test is the inside straight leg lift. The patient lies on the affected side and then flexes the unaffected knee to about 90 degrees and plants the foot of the unaffected extremity on the exam table to provide support. From this position, the patient attempts to lift the injured leg using adduction. Inability to lift the injured leg against gravity suggests severe injury. With milder injuries, the examiner can place light resistance against the medial ankle while the patient lifts the leg to assess relative adductor strength.

●Functional testing of the abdominal muscles.

Ask the patient to assume a position with the hips flexed approximately 45 degrees, knees flexed approximately 90 degrees, feet planted on the examination table, and arms folded across the chest. Starting from this position, the patient performs a partial sit-up, lifting their head and scapulae off the examination table, while you brace the patient's knees with one hand and arm and press the other arm against their chest (picture 6). Exert enough resistance to balance the sit-up.

From the same position, have the patient perform an oblique sit-up, moving one shoulder towards the opposite knee while you provide resistance by pressing against this shoulder.

When functional abdominal testing causes significant pain, this suggests a more complex injury of the inguinal region than an isolated adductor injury. Such injury often involves the conjoint or abdominal tendons, in addition to the adductor tendons. (See "Sports-related groin pain or 'sports hernia'".)

●Functional testing of the iliopsoas muscle.

Have the patient flex their hips and knees as much as possible. Next, try to extend the patient's flexed hip against their resistance by pulling it with a hand wrapped around the femur just proximal to the knee (picture 7). Pain elicited by this test suggests that the primary injury involves the hip flexors as well as adductors.

●Thomas test (modified) for iliopsoas.

Begin with the patient supine with both legs, from the knee distally, hanging off the end of the examination table. Then have the patient flex one hip by clasping the knee with both hands and pulling it down to his chest. The other leg remains relaxed, hanging off the end of the table. While flexing the hip, the patient should lift his head and shoulders as far as possible off the table. The examiner stands at the end of the table supporting the position by pressing the side of his trunk against the foot of the flexed leg (picture 8). The position of the extended leg is recorded as "tight" if the thigh is elevated off the table (ie, long axis of the femur angles upward towards the ceiling (picture 9)), and "not tight" if it remains at the level of the table or angles downward towards the floor.

The examiner then places one hand on the femur of the hanging leg just above the knee and presses the leg down to stretch the iliopsoas passively. When the stretch is felt to be "maximal," pain is recorded as "yes" or "no." A positive test suggests that hip flexor tightness likely contributed to the adductor injury.

●Passive and active range of motion of the ipsilateral hip and knee are assessed and compared with the contralateral extremity to identify painful or limited range of motion. In addition, impingement and apprehension tests of the hip joints are performed.

In addition to a careful assessment of the adductor muscles and tendons, and other relevant musculoskeletal structures (eg, hip joint), it is important not to overlook the possibility of conditions unrelated to the musculoskeletal system that may account for the patient's symptoms. This is particularly important when the diagnosis is not clear-cut based on the history and preliminary examination findings or when pain may be referred. In such cases, a more extensive examination is indicated, including the following:

●Examination of the inguinal canal and conjoint tendon for incipient hernia. (See "Classification, clinical features, and diagnosis of inguinal and femoral hernias in adults", section on 'Physical findings'.)

●Examination of the abdomen, lower back, and genitourinary system. (See "Evaluation of the adult with abdominal pain", section on 'Physical examination' and "Evaluation of low back pain in adults", section on 'Initial evaluation'.)

DIAGNOSTIC IMAGING

Overview and approach — In many cases, the diagnosis of adductor muscle strain is straightforward and based solely on the history and physical examination. In such cases, diagnostic imaging is not necessary. Clinicians facile with musculoskeletal ultrasound often perform an ultrasound examination as part of their standard assessment of suspected muscle or tendon injuries. Ultrasound can be useful for determining the exact location and extent of the injury, and for monitoring recovery [33]. When the diagnosis is less clear or there are concerning alternative diagnoses that must be ruled out, imaging studies are obtained. Generally, plain radiographs of the pelvis are the initial studies. Magnetic resonance imaging (MRI) is performed when a definitive diagnosis is required.

Plain radiographs — Anteroposterior (AP) (image 1)and lateral plain radiographs of the pelvis are useful for assessing skeletal anatomy, excluding larger avulsion fractures and apophyseal injuries, and evaluating skeletal maturity based in part on the patency of the physes. If coexisting hip pathology (eg, fracture, slipped capital femoral epiphysis) is suspected, additional views may be needed.

Plain radiographs are indicated in the following settings:

●Palpation reveals tenderness around the symphysis pubis or pubic rami

●Adolescent patient with a suspected avulsion injury (eg, acute injury, bony tenderness)

●Signs of hip involvement present (eg, osteoarthritis [OA], impingement)

●Direct trauma may have resulted in myositis ossificans (heterotopic ossification within muscle) (see "Quadriceps muscle and tendon injuries", section on 'Myositis ossificans')

●Persistent pain (eg, >2 weeks unremitting) despite rest from inciting activity and appropriate treatment of the soft tissue adductor injury or night pain

Musculoskeletal ultrasound

Technical aspects — For imaging the adductor muscles and tendons, we suggest using a high-frequency transducer (7 to 17 mHz) probe because it provides superior definition (higher frequency provides better resolution but does not penetrate as deeply).

Linear transducers have a straight probe surface in contact with the patient. In thinner patients this may work well for adductor imaging. However, a curved anatomic surface may create a loss of transducer-skin contact and make the scan more difficult to perform. Due to the anatomical contour of the groin region, loss of contact between the patient's skin and transducer creates sound dropout artifacts. A curvilinear high-frequency transducer may be useful if such problems are encountered. With either type of probe, the examiner uses the hyperechoic appearance of the bones at the pubic symphysis to locate tendon insertions and guide adjustments in image quality.

Occasionally, a transducer typically used for abdominal imaging is needed to obtain the required depth in large patients. This approach allows for greater penetration of tissues but at the cost of decreased resolution.

Positioning and basic performance — To image the adductor region, the patient should be placed supine with the hip slightly externally rotated and the knee slightly bent (picture 10). The degree of external rotation and knee flexion can be varied during the examination. The uninjured side can be used for comparison.

The common adductor origin is a short tendon that runs from the pubic bone to the musculotendinous junction (MTJ) of the adductors. If normal, the tendon appears light grey on two-dimensional (2D) imaging.

Anisotropy means that ultrasound images depend upon the direction of the sound waves (image 2). This feature of ultrasound can produce a false hypoechoic appearance in the tendon and is impossible to eliminate completely. Toggling the transducer with a "heel-toe" technique can minimize this effect. The technique involves applying pressure and a tilt selectively to one end of the transducer more so than the other.

Using the straight face of a linear high-frequency transducer on curved anatomy—the pubic bone—causes loss of skin contact along sections of the transducer and thus loss of returning echoes to the transducer. It is therefore necessary to manipulate the transducer around the anatomic curve so that each section of the tendon or muscle is imaged at right angles to the direction of the sound beam. Accommodating the curve and avoiding anisotropy is done to try to bring tendon fibers as near to parallel to the transducer face as possible.

Increased Doppler flow and the presence of neovessels are confirmatory evidence that any hypoechoic change seen represents muscular injury, swelling, or retraction rather than anisotropic change. To assess the tendon volume, the injured and contralateral tendons are compared.

Appearance of injured tissue — Hypoechoic regions within the tendon may represent inflamed, swollen, torn, or granulomatous tissue (image 2). Hyperechoic regions correspond to fibrotic scar tissue or calcification. If shadowing is seen, calcification is almost certainly present.

The examiner should look for complete distraction of the tendon off the pubic bone and intervening fluid, which will be hypoechoic and can be displaced with transducer pressure. A grey swirling appearance represents liquid hematoma (image 3). When organized, a hematoma is noncompressible and shows varying shades of grey from charcoal to white. Any distraction defect should be measured.

In chronic tendinopathy, the cortical contour of the pubic bone may be irregular; the contralateral side may be used for comparison unless symptoms are bilateral which may occur in chronic cases.

The symphysis pubis is assessed for cortical irregularity (image 4) and hypertrophy/edema of the transverse ligament. This can indicate pelvic instability as part of a complex athletic pubalgia problem.

Enlarged lymph nodes should be noted (image 5 and image 6), as these suggest reactive lymphadenopathy of disease (eg, infection, lymphoma, metastases).

Distal to the common tendon, the MTJ and proximal muscle belly are assessed for:

●Edema – The muscle appears more hypoechoic than normal.

●Intramuscular bleeding – This increases the echogenicity of the muscle as the blood clots and causes a "hazy" appearance of the muscle fibers.

●Partial tear – Disruption of the normal organized architecture of muscle belly represents a small defect (image 7).

●Complete tear – Fluid filled defect with distraction of the muscle stumps (image 8); liquid or organized hematoma will fill the gap depending on how many hours or days old the tear is. It is important to measure the distraction defect. Follow-up scans should be performed and measurements obtained to monitor healing.

Magnetic resonance imaging (MRI) — Given the improving sensitivity and relatively low cost of ultrasound, MRI scans are generally not necessary for evaluating most adductor injuries. Indications for MRI include:

●Suspected avulsion (typically adolescent patients with symptoms and signs localized to bony origin or insertion of adductors).

●Complex injuries involving more than one structure.

●Injuries that fail to progress as expected despite compliance with an appropriate rehabilitation program.

●Patients with a history of chronic or recurrent groin pain in which the diagnosis remains in question after examination and standard imaging (eg, plain radiographs, ultrasound).

In cases where recovery is not proceeding as expected or the diagnosis remains in doubt, MRI can help to exclude bone stress injury, hip labrum tears, avascular necrosis, osteomyelitis, and malignancy. MRI demonstrates high sensitivity and specificity for bone, cartilage, muscle, and tendon injuries in the groin region [34,35]. MRI is the only technique capable of assessing groin injuries involving this wide range of tissue types and across the full spectrum of injury severity.

Disruption of muscle or tendon fibers causes hyperintensity on fat-saturated, fluid-intense MRI sequences. Associated findings with adductor injuries may include bone edema of the pubic symphysis, bony avulsion lesions, and a "secondary cleft sign" (a curvilinear image that is continuous with the symphysis pubis). A continuation between a physiologic fluid-filled cleft in the pubic symphysis and a pathologic secondary cleft in the symphyseal fibrocartilage on short T1 inversion images (STIR) may represent a break in the pelvic ring due to chronic stress or injury of the rectus abdominus tendon and adductor tendon insertions [2,34]. Proximal adductor avulsion is rarely isolated and usually involves injury to the pyramidalis-anterior pubic ligament-adductor longus complex and pectineus, leading to the acronym "PLAC" [36].

DIAGNOSIS — Adductor injuries can generally be diagnosed on the basis of the clinical presentation and a careful examination, as described above. Musculoskeletal ultrasound is often useful for confirming the clinical diagnosis. When a more definitive diagnosis is required, magnetic resonance imaging (MRI) is performed, but this is usually unnecessary. Although there is a degree of overlap among the different types of adductor injury, the cardinal findings of each are distinct and summarized below:

Adductor muscle contusions — Adductor contusions are caused by a direct blow to the muscles and present with tenderness, swelling, and, depending on the severity, visible bruising over the affected area. Function is variably affected and there is some degree of weakness to resisted hip adduction in particular.

Adductor muscle strains (minor tears) — Minor adductor muscle tears (grade 1) may be acute (athlete remembers specific trauma causing injury) or insidious (athlete notes pain or dysfunction upon completion of activity) in onset. The affected area is tender to palpation and resisted hip adduction reproduces pain. The injured adductors are weaker than the unaffected side, but the discrepancy may be small. (See 'Grade of injury' above.)

Adductor muscle tears — Substantial adductor muscle tears (grade 2 or 3) occur acutely during a high-risk movement (eg, sprint, sudden change in direction at high speed [cutting], or exaggerated stretch during sport) and usually force the athlete to stop training or competing immediately. There is often a noticeably antalgic gait, the involved area is tender and ecchymotic. A defect or hematoma may be palpable. Resisted hip adduction is almost always markedly compromised and painful. Clinicians facile with musculoskeletal ultrasound can perform an examination to confirm the clinical diagnosis. (See 'Overview of injury types and related mechanisms' above and 'Physical examination' above and 'Musculoskeletal ultrasound' above.)

Adductor tendon overuse injuries — Chronic adductor tendon injuries (tendinopathy) are gradual in onset, typically developing over weeks to months of overuse. Athletes often complain of pain at the start of running-associated exercise. Higher-grade tendon injuries persist during running and are exacerbated by cutting, jumping, acceleration, and deceleration maneuvers. Both proximal and distal adductor tendons may be involved; palpation of the affected portion of the tendon elicits pain. Resisted hip adduction reproduces pain to varying degrees depending upon the severity of the injury. Clinicians facile with musculoskeletal ultrasound can perform an examination to help confirm the clinical diagnosis. (See 'Clinical presentation' above and 'Physical examination' above and 'Musculoskeletal ultrasound' above.)

Adductor avulsion injuries — Avulsion injuries of the adductor tendons occur acutely and are associated with forced adduction, often against resistance. Nearly all involve the proximal tendon origin. The athlete may describe a "popping" sensation associated with severe pain. The athlete is significantly incapacitated and often unable to bear weight. Significant bruising appears within hours in the area of the avulsion. The cord or band comprising the proximal adductor longus tendon that is easily palpated with the hip abducted in normal circumstances is no longer discernible, and often the patient cannot perform hip adduction against even the slightest resistance. Placing the lower extremity in a position with the hip abducted causes great discomfort. (See 'Presentation and examination findings of particular injuries' above.)

DIFFERENTIAL DIAGNOSIS — Alternative diagnoses to be considered in the patient with a suspected adductor injury include those listed below [2]. It is worth emphasizing that any child aged 2 to 15 years with groin pain and an antalgic gait, especially if fever is present or reported, warrants urgent investigation. Possible diagnoses include avascular necrosis of the hip, Legg-Calvé-Perthes disease, septic arthritis, and slipped capital femoral epiphysis (SCFE). Early orthopedic consultation is appropriate. The evaluation of such children is reviewed in detail separately. (See "Approach to hip pain in childhood".) A table listing potential diagnoses for adults presenting with groin pain is provided (table 1).

●Muscle and tendon conditions

•Athletic pubalgia or "sports hernia" – Athletes with a sports hernia typically complain of unilateral groin pain that developed insidiously, improves once the athlete has warmed-up but recurs when the athlete becomes fatigued. Increased intra-abdominal pressure (eg, from valsalva maneuver or sit-up) often exacerbates the pain. The adductor muscles and tendons are not tender, but resisted hip adduction may reproduce symptoms. Ultrasound imaging of the adductor muscles and tendons may reveal no abnormality, but a subset of athletic pubalgia patients has associated adductor tendinopathy. The key distinguishing ultrasound finding is the presence of pathology above the inguinal ligament. (See "Sports-related groin pain or 'sports hernia'".)

•"Osteitis pubis" – Refers to an inflamed symphysis pubis often associated with pubic instability syndrome; tenderness is focal directly on the symphysis, rather than the adductors, which are nontender. Chronic pubic instability may be associated with adductor overload and tendinopathy; pain is elicited by provocative maneuvers and by palpating the external inguinal ring. AP view radiographs of the pelvis often reveal changes suggestive of osteitis pubis and help to confirm the diagnosis. (See "Osteitis pubis".)

•Lower abdominal muscle strains may be part of an athletic pubalgia or may occur in isolation. With acute injuries, a history of abdominal strain or trauma is typical. Tenderness is maximal proximal to the pubic rami and elicited by resisted sit-ups. The adductors are nontender and ultrasound imaging of the adductor muscles and tendons reveals no abnormalities. (see "Approach to hip and groin pain in the athlete and active adult")

●Bone conditions

•Stress fractures of the pelvis and femoral neck may refer pain to the adductor region. Weight-bearing and especially hopping are difficult and reproduce the pain whereas adductor palpation and resisted hip adduction cause minimal, if any discomfort. Appropriate imaging identifies most stress fractures. (See "Overview of stress fractures", section on 'Diagnosis' and "Femoral stress fractures in adults".)

•Apophysitis occurs in active adolescents and exercise-associated pain may be felt at any of the apophyses around the pelvis including the anterior superior iliac spine, anterior inferior iliac spine, and inferior pubic rami. Tenderness is localized to the bony origins, rather than the tendons and muscles. Ultrasound imaging of the adductor muscles and tendons reveals no abnormalities. Ultrasound findings of increased hypoechoic change and widening of the secondary ossification center compared with the opposite side strongly suggest the diagnosis.

●Nerve injury

•Ilioinguinal nerve entrapment – The ilioinguinal nerve arises from the T12 to L2 nerve roots. Ilioinguinal nerve entrapment causes a lower abdominal pain syndrome characterized by muscular-type pain at the iliac fossa with a characteristic radiation pattern typically involving the groin and thigh, and altered sensation at the cutaneous area innervated by the ilioinguinal nerve (medial groin area including upper scrotum in men and labia in women) [37,38]. There may be a past history of herniorrhaphy or other lower abdominal surgery. According to several reports, a focal trigger point medial and below the anterosuperior iliac spine (ASIS) is common, and relief of pain with injection of a local anesthetic just medial to the ASIS confirms the diagnosis. The adductors are nontender and ultrasound imaging of the adductor muscles and tendons reveals no abnormalities.

•Obturator nerve entrapment – The obturator nerve arises from the posterior division of nerve roots L2 to L4 and runs over the pelvic rim into the lesser pelvis (figure 17). Entrapment usually occurs at the level of the obturator foramen and proximal thigh where fascia compresses the anterior branch of the nerve as it passes over the adductor brevis muscle. Symptoms typically begin insidiously as deep groin pain centered around the adductor origin. Hip adduction weakness may be present if the nerve is sufficiently injured. Definitive diagnosis is made by electromyography (EMG) and nerve block. (See "Overview of lower extremity peripheral nerve syndromes", section on 'Obturator nerve'.)

●Hip pathology

•Femoroacetabular impingement – Pain stemming from femoroacetabular impingement is generally focused more lateral of the inguinal region and can often be elicited with impingement testing, particularly with the hip in a position of femoral adduction and internal rotation (FADIR). Palpation and provocative testing of the adductors do not reproduce symptoms, but associated adductor strains may occur. (See "Femoroacetabular impingement syndrome".)

•Labral tears – Pain from tears of the hip labrum is generally focused around the hip joint but may refer to the groin area. Pain is elicited with the adductors in a relaxed position while the hip joint is loaded in a FADIR position. Advanced imaging or arthroscopy is needed to make a definitive diagnosis. (See "Approach to the adult with unspecified hip pain".)

•Chondral lesions – Unless the patient has compensated in a way to create adductor strain, chronic intra-articular chondral lesions would not likely be associated with specific adductor weakness or pain with strength testing. More general hip motions and loading the hip joint would produce pain, suggesting that the primary pathology is in the joint and not muscular. (See "Approach to the adult with unspecified hip pain".)

•Osteoarthritis (OA) of the hip joint – Pain from OA often refers to the groin region, but the adductors remain nontender, and adductor strength is not diminished. (See "Approach to the adult with unspecified hip pain".)

●Tumors – Although not commonly mistaken for adductor injury, benign and malignant tumors of muscle or bone can develop in the area of the adductors and clinicians should be aware of such possibilities when considering the differential diagnosis [39,40]. Such tumors often present with pain or discomfort not associated with exercise. If there is no history of trauma or acute injury, provocative maneuvers fail to elicit notable increases in discomfort, and pain persists despite rest, it is prudent to obtain imaging to avoid missing these diagnoses.

●Conditions causing referred pain ‒ In rare cases, referred causes of pain may mimic adductor injury. These can include pain referred from lumbar radiculopathy and from infectious conditions of the abdomen or pelvis or pathology affecting the sacroiliac joint area. (See "Acute lumbosacral radiculopathy: Etiology, clinical features, and diagnosis".)

INDICATIONS FOR ORTHOPEDIC CONSULT OR REFERRAL — Any avulsion or suspected avulsion injury of an adductor tendon should be referred to an orthopedic surgeon for evaluation and possible surgical reattachment. Adductor function is significantly compromised without a firm attachment and referral should be made as soon as possible (within a few days) following such injury. Over days to weeks, the avulsed musculotendinous unit retracts and surgery becomes more difficult. While some authors have suggested that nonoperative management allows for a quicker return to play and lower complication rate for proximal adductor tendon ruptures, surgical referral remains prudent [41]. Typically, pediatric avulsion injuries are treated more conservatively, but orthopedic consultation is still recommended.

High-grade and complete (grade 3) tendon tears may require surgery and referral to an orthopedic surgeon is warranted. The same holds true for chronic injuries (≥3 months duration) of the adductor longus origin, which may also involve the conjoined tendon and/or be part of a complex injury, such as sports hernia. A variety of injuries have been noted during the surgical exploration of athletes with chronic groin pain [42]. If there is any doubt about the extent of such injuries, referral to a surgeon experienced in the repair of these tendons is indicated. (See "Sports-related groin pain or 'sports hernia'".)

If, during the course of conservative treatment, an adductor injury does not appear to be healing appropriately after three months despite compliance with an appropriate rehabilitation program, orthopedic consultation is warranted.

MANAGEMENT OF ADDUCTOR INJURIES

Initial treatment: — The basic principles of care for soft tissue injury apply to all adductor injuries [43]. These are summarized in the mnemonic POLICE: protection, optimal loading, ice, compression, and elevation. The patient should be placed in a resting position (supine with hips slightly flexed and supported with cushions) or on crutches when moving. Hip abduction should be avoided. Crushed ice (covered, not directly applied) can be compressed against the injured area for up to 20 minutes every one to two hours; this treatment may be continued for 48 hours. Iced water machines (eg, CryoCuff or Game Ready) may be used. Compression of the injured tissue using a 6-inch (15-cm) elastic bandage roll, elastic bandage sleeve, or compression pants help to limit bleeding and provides support. Bandage rolls should be snug but not so tight as to compromise circulation. Over-the-counter analgesics may be used for pain relief. (See "Nonselective NSAIDs: Overview of adverse effects", section on 'Healing of musculoskeletal injury'.)

Rehabilitation

Overview — It is appropriate to begin physiotherapy after acute bleeding has stopped, usually 48 to 72 hours after an acute injury is sustained. Before this time, ice and compression are applied as above and techniques (eg, gentle massage) may be used to relieve spasm in surrounding muscle groups. (See 'Initial treatment:' above.)

Crutches and limited weight-bearing protect the injured adductors from excessive loading, as injury reduces the ability of soft tissue to tolerate functional loads. The primary goal of treatment is to restore this ability. This is achieved using methods that support each phase of soft tissue healing. These phases, in chronological order, include inflammatory, repair, and remodeling. The overall aim is to achieve a functional scar, with scar tissue of similar length, mobility, and capacity to handle loads as the uninjured tissue [6].

During the inflammatory phase, treatment is aimed at decreasing inflammation (eg, POLICE, immobilization or gentle mobilization depending on the injury) and reducing pain (gentle myofascial release of protective muscle spasm, taping (picture 11), analgesics). In the repair phase, treatments are used to help orient collagen fibers and increase the amount of collagen in the developing scar tissue. Treatments used during the repair and remodeling phases include joint and soft tissue mobilization, myofascial release, mechanical and proprioceptive support through taping, stretching, reeducation of motor control, and strengthening of the injured muscle and related kinetic chain. A basic rehabilitation program for acute uncomplicated adductor muscle and tendon strains (grade 1 and less severe grade 2 injuries) is provided in the attached table (table 2); preferred exercises for specific adductor injuries that may be used in the basic program are described below. (See 'Area-specific adductor injury rehabilitation' below and 'Grade of injury' above.)

An important aspect of treatment is assessment of the patient's posture and movement patterns to identify factors that may have predisposed to the injury or were caused by the injury. Recognizing and addressing these biomechanical flaws are crucial to successful rehabilitation and prevention of recurrence.

Area-specific adductor injury rehabilitation

Exercise guidelines for all injuries — The following interventions are important for recovery:

●Relative rest: Abstain from activities that cause pain or stress the tendon.

●Isometric exercises for initial pain management.

●Eccentric exercises to strengthen the tendon and facilitate tissue regeneration.

The patient should understand that loading the muscle and tendon during these exercises, particularly eccentric strength exercises, will cause discomfort (Visual Analogue Scale 3-4/10). However, following the exercise (particularly the following day) there should be no pain or minimal pain at most. If there is severe pain during the exercise, the patient should stop and the exercise should be modified or replaced. If there is significant pain the day after exercise, the load should be reduced and then gradually increased as patient tolerance and strength improve. A training log can be useful in this regard.

Throughout rehabilitation, support of the adductor muscles is reasonable. This may be accomplished with a muscle sleeve (picture 12) or elastic bandage (picture 11).

The abdominal, hip, and hamstring muscles play essential roles in providing dynamic stability whenever the athlete is in a single leg stance, and exercises to strengthen these muscles, as well as the adductors, should not be overlooked during rehabilitation. This can be accomplished with exercises, such as the single leg squat and the lunge [44-46].

Adductor muscle tears — Preferred exercises for the rehabilitation of muscle strains include those below. Performing these exercises should not be particularly painful; there may be some tenderness post-exercise.

●Isometric hip adduction with ball between bent knees; progression to ball between ankles (picture 13 and picture 14).

●Side-lying hip adduction (picture 15).

●Standing hip adduction against resistance (picture 16).

●Side lunge (picture 17).

Adductor tendon tear — It is important to begin rehabilitation exercises using a shorter lever when treating a tendon tear, in comparison with a muscle tear. The shorter lever reduces stress and pain at the tendon insertion. As an example, bent rather than straight knees may be used when performing the initial variation of an exercise such as a plank. In addition, closed chain exercises may cause less discomfort in the early phases of rehabilitation.

Preferred exercises for the rehabilitation of tendon tears include:

●Isometric adduction with ball between bent knees; progression to ball between ankles (picture 13 and picture 14).

●Standing hip adduction against resistance (picture 16) – Standing adduction exercises incorporate eccentric loads on the return phase of the exercise and should be performed in a controlled manner.

●Side lunge (picture 17).

●Single-leg squat (picture 18).

●Side plank with adduction (picture 19) – This is likely to be painful in the early phase and should probably be incorporated after base strength has increased. Start with bent legs and progress as pain allows.

Adductor enthesopathies — With any enthesopathy, the musculotendinous unit needs to be loaded specifically (eg, isometric adduction, standing adduction). Preferred exercises for the rehabilitation of enthesopathies include the following:

●Isometric adduction with ball between bent knees (picture 13).

●Standing hip adduction against progressive resistance (picture 16) – Standing adduction exercises incorporate eccentric loads on the return phase of the exercise and should be performed in a controlled manner.

●Side plank with adduction (picture 19) – This is likely to be painful in the early phase and should probably be incorporated after base strength has increased. Start with bent legs and progress as pain allows.

●Side lunge and single leg squat (picture 17 and picture 18).

Final stage of rehabilitation and return to sport — Before resuming full sport, the athlete recovering from an adductor injury should demonstrate functional strength and stability. Functional exercises that can be used during this final stage include the following:

●Single-leg jump onto soft unstable surface (eg, Bosu ball) and step off (picture 20).

●Single-leg balance on unstable surface and catch balls thrown from different angles (picture 21).

●Single-leg side jump on and off unstable surface (picture 22).

●Single-leg side jump between unstable surfaces (identical to exercise above except athlete jumps between two unstable surfaces).

●Single-leg hop in four quadrants: clockwise; counter clockwise; diagonal (picture 23).

●Single-leg figure-of-eight hops (similar to exercise above except athlete hops in the shape of an "8").

●High knee runs on trampoline.

For all adductor injuries, it is imperative that rehabilitation ultimately include sport-specific and dynamic exercises. These should incorporate changes in speed, cutting and turning, and single leg stability. The exercises should exhibit the control learned during the earlier phases of rehabilitation and applied functionally.

Athletes performing rehabilitation for acute adductor muscle and tendon injuries may return to sport based on clinical criteria, including pain-free completion of clinical assessments and sport-specific drills [47]. Clinical assessments often include muscle and tendon palpation, active and passive stretch, isometric and dynamic muscle contraction against resistance, Copenhagen exercises (see 'Prevention' below), linear sprinting, and agility tests (eg, T test, which involves a sprint, side shuffle, and backward run). Criteria guided by appropriate clinical assessments and including sport-specific activities appear to be more effective at reducing the risk of reinjury following return to sport than basing decisions on initial magnetic resonance imaging (MRI) injury grading.

Isokinetic testing of adductor strength — Isokinetic testing is useful for determining baseline strength in the uninjured athlete or early during rehabilitation to help gauge progress (eg, using serial strength measurements) or to use as a rehabilitation exercise itself. The isokinetic apparatus (eg, Biodex machine (picture 24)) has an accommodating resistance whereby the load applied to the muscle-tendon unit in question varies according to the patient's effort. The more force the patient applies, the greater the resistance. This allows the muscle-tendon unit to work throughout its entire range of motion without pain. However, isokinetic training on such an apparatus cannot mimic the functional environment of sport and therefore, must be used in conjunction with a comprehensive rehabilitation program.

Side-lying adduction/abduction is performed at a torque of 60 and 120 degrees per second and measures speed (picture 25). The speed is set for the test so that it does not become a variable in the testing. Higher speeds more closely mimic the activation and time to contraction in sports that involve sharp cutting and pivoting movements. This test does not have standardized norms for performance, and the range is fairly limited in abduction for many athletes. Therefore, the test is generally best used to compare the peak torque generated at initial and follow-up testing.

Chronic adductor injuries — In athletes who recall no specific injury but experience chronic adductor-related pain when playing, a modified approach may be required [48]. Management includes a physical therapy program incorporating a similar approach to that described above.

In some cases, athletes with chronic adductor pain during sport may be permitted to continue playing. Factors influencing a medical team's decision regarding ongoing participation while treating a chronic adductor strain include:

●Functionality of the player (is performance compromised).

●Stage of the season (more conservative early on).

●Objective stress testing (adductor squeeze test results compared with pre-season findings).

In sports such as soccer (football) or American football, many high-level athletes continue to play with adductor-related pain during the competitive season. Chronic residual pain from a prior adductor muscle or tendon injury is often the source, and such athletes typically need to continue performing rehabilitative functional exercises throughout the season to lessen the risk of further injury. As an example, coaches and athletic trainers may use drills that emphasize cutting with gradually increasing speed as part of the warm-up prior to any practice or contest. Consistent use of compression sleeves, wraps, or taping can be helpful. Such chronic injuries are unlikely to resolve completely until the competitive season ends.

Adductor contusions — Adductor contusions are treated initially with intensive icing and compression to reduce pain and minimize swelling and any associated hematoma. Any exercises are delayed for 48 hours, or possibly several days for more severe injuries, while the contusion resolves. Crutches may be used initially for larger or more painful contusions. Once pain is minimal, the patient can gradually resume activity.

Other treatments

Platelet rich plasma (PRP) injections — Several growth factors have been found to enhance muscle regeneration in vitro, but in vivo studies are limited, and few high-quality randomized trials have been performed to assess this treatment. While some analyses report benefit from PRP injection of tendinopathy, the evidence in adductor injuries remains limited to observational studies, and results are mixed [49,50]. The treatment of musculoskeletal injuries with PRP is discussed separately. (See "Overview of the management of overuse (persistent) tendinopathy", section on 'Autologous blood and platelet-rich plasma injection' and "Biologic therapies for tendon and muscle injury".)

Surgery — Surgery is rarely necessary with adductor muscle or tendon injuries and is reserved for complete avulsions (usually at the adductor longus origin) or chronic tendinopathy that has not responded despite full compliance with a well-designed rehabilitation program over several months [51,52]. In a 16-year study of Union of European Football Associations (UEFA) soccer athletes with adductor injuries, 4 percent required surgery [53]. A systematic review of surgical versus conservative management of traumatic proximal adductor longus avulsion injuries (n = 46) concluded that both treatments enabled patients to resume their preinjury activity level, but that surgically treated patients required a longer time to return to sport [54].

FOLLOW-UP CARE AND PROGNOSIS — Injured athletes in a team environment are likely to be followed daily by the medical team or an athletic trainer and receive daily treatments. Outpatient physiotherapy is optimally performed two to three times a week for the first three to four weeks. Gradually, the emphasis shifts to a return to sport as rehabilitation progresses, pain diminishes, and functional abilities improve.

Recreational athletes and individuals in an occupational setting likely will have limits on how frequently they can access medical care. Weekly or biweekly follow-up is helpful to guide their return to activity, unless they are referred for formal physical therapy.

Subjective feedback from the athlete about symptoms and how they are coping with activities of daily living, as well as more objective criteria, such as responses to clinical stress tests, isokinetic testing, and functional loading (eg, incremental running, cutting, and plyometric drills), are all used by the clinician when deciding whether to advance to more demanding exercises.

Once the injury has healed and the athlete is to start a program designed to return them to play, it is important to include functional groin exercises among the activities. Such exercises are described above. Once the athlete returns to play, prevention should be emphasized. We suggest that all athletes recovering from an adductor muscle or tendon injury perform sport-specific functional groin exercises daily for the first three months after return to sport. After three months, the athlete should be reevaluated by a sports physician, physiotherapist, athletic trainer, or comparable professional and plans made for continuing injury prevention.

Prognosis varies depending upon the extent of injury and patient activity [13]. In general, grade 1 adductor muscle or tendon strains require between 10 and 21 days until the patient reaches the final phase of rehabilitation (functional training) and begins their return to sport activity, grade 2 injuries require four to six weeks, and grade 3 tears or avulsions may require two to three months or possibly longer.

In a prospective observational study with follow-up for approximately 50 male athletes with adductor injury, physical examination findings associated with longer healing times before return to play were palpable tenderness or a defect at the proximal adductor longus insertion [55]. Overall, the timing for return to play was highly variable, ranging from 4 to 11 weeks. Magnetic resonance imaging (MRI) that showed injury at the bone-tendon interface was associated with longer healing times but predicted the same range for return to play and did not add significant value to the clinical examination. For athletes with injuries but no palpable pain at the adductor insertion, the average return to play was two to four weeks. This study confirms previous clinical estimates for grade 1 to 3 injuries while reinforcing that neither clinical examination nor MRI allows precise determination of return to play.

PREVENTION — Simple exercises incorporated into preseason and in-season training can reduce the incidence of adductor injuries [13,56]. One such program is the Copenhagen Adductor (CA) exercise intervention, which consists of three basic exercises that progress in difficulty (picture 26) [57].

●Basic exercise – Lying adductor leg raise (picture 26)

●Intermediate exercise (movie 1)

●Advanced exercise (movie 2)

In a cluster-randomized trial involving 35 semi-professional football (soccer) teams (652 players), the average prevalence of groin injury was significantly lower among teams assigned to perform the Copenhagen Adductor program (13.5 percent [95% CI 12.3-14.7] versus 21.3 percent [95% CI 20.0-22.6]) [58]. The results of a subsequent small randomized trial in male soccer players suggest that the Copenhagen program's benefits stem from improved adductor flexibility and increased muscle thickness [59].

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: General issues in muscle and tendon injury diagnosis and management" and "Society guideline links: Muscle and tendon injuries of the lower extremity (excluding Achilles)" and "Society guideline links: Hip and groin pain".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topic (see "Patient education: Groin strain (The Basics)")

SUMMARY AND RECOMMENDATIONS

●Adductor function and anatomy – The function of the adductor muscles is to adduct the hip and assist in stabilizing the pelvis. Their function is intrinsically linked with the abdominal and pelvic muscles. Acute injuries of the adductor muscles and tendons, primarily muscle strains, are relatively common, especially in sports involving rapid acceleration and change of direction. The adductor longus is the adductor muscle most commonly injured due to its relative length, greater tendon to muscle ratio, and weaker pubic attachment. (See 'Anatomy and biomechanics' above and 'Classification' above.)

●Epidemiology and risk factors – Sports that place greater demands on the adductor muscle group, in particular more frequent eccentric contraction, appear to have a greater incidence of adductor injuries. These sports include soccer (football) and ice hockey. A number of potential intrinsic and extrinsic risk factors may contribute, including decreased strength ratio of hip adductors to abductors, decreased hip abduction mobility, poor conditioning, muscle fatigue, inadequate warm-up, and particular biomechanics (eg, skating style technique for cross-country skiing). (See 'Epidemiology and risk factors' above.)

●Mechanism of injury – Common mechanisms for adductor muscle and tendon strains include: rapid adduction of the hip against an abduction force (eg, sudden rapid change of direction during sport), acute forced abduction that stretches the adductors (eg, stretching to make a tennis shot), and sudden acceleration with sprinting. (See 'Mechanism of injury' above.)

●Clinical presentation

•Acute adductor strain and contusion – Adductor muscle or tendon strains (tears) and muscle contusions are common causes of groin pain. Low-grade, minor adductor muscle strains are characterized by the absence of bruising, tenderness over the injured muscle but without a palpable defect, and pain with resisted adduction but minimal loss of power. More severe muscle strains are characterized by a clear onset of injury when the athlete was forced to stop participating, antalgic gait, bruising and tenderness at the injury site, possibly a palpable defect in the muscle belly (or tendon), and notable pain and weakness with resisted hip adduction. Adductor contusions are caused by a direct blow to the muscle and manifest as bruising, swelling, and local pain and tenderness. (See 'Clinical presentation' above.)

•Adductor tendon avulsion – Adductor tendon avulsions are uncommon. Detachment of one or more of the adductor muscles from its origin at the pubic ramus causes immediate and sustained dysfunction. Athletes may recall a "pop" while sprinting or cutting or at the time of direct contact. Gait is severely restricted or impossible. Examination reveals proximal bruising, significant tenderness along the pubic ramus, a palpable defect proximally, and distal swelling over the retracted muscle.

•Adductor tendinopathy – Chronic adductor tendinopathy develops over weeks to months from repetitive loading with inadequate recovery time. Rather than recalling a specific incident, the athlete may describe a change in routine (eg, increased training volume) or increased performance of certain exercises over time, such as cutting or sprint drills, leading up to the injury. Tenderness is present over the adductor tendon extending proximally from the medial epicondyle. Power may be diminished but not as significantly as with muscle tears.

●Clinical evaluation and diagnostic imaging – In many cases, the diagnosis of adductor muscle or tendon strain is straightforward and based solely on the history and physical examination. In such cases, diagnostic imaging is not necessary. Clinicians skilled with musculoskeletal ultrasound often perform an ultrasound examination as part of their standard assessment of suspected muscle or tendon injuries. Plain radiographs may be obtained to rule out bony injury (eg, large avulsion fracture); magnetic resonance imaging (MRI) may be performed when a definitive diagnosis is required. (See 'Performance of the examination' above and 'Diagnostic imaging' above and 'Musculoskeletal ultrasound' above.)

●Differential diagnosis – The differential diagnosis for adductor injury includes athletic pubalgia (sports hernia), osteitis pubis, low abdominal muscle strains, stress fractures, apophysitis, nerve entrapment, femoroacetabular impingement, hip labrum tears and chondral lesions, and osteoarthritis (OA). Clinical features that can help clinicians distinguish among these conditions are described in the text. (See 'Differential diagnosis' above.)

●Indications for orthopedic referral – Assessment of the patient by an orthopedic surgeon is needed for any adductor tendon avulsion injury, or when such injury is suspected, any high-grade or complete tendon tear, complex injuries such as "sports hernia" and any adductor injury that does not appear to be healing appropriately after three months despite compliance with an appropriate rehabilitation program. (See 'Indications for orthopedic consult or referral' above.)

●Management – The management of most adductor muscle and tendon strains consists of physical therapy. Treatment, including a basic rehabilitation program for muscle strains and descriptions of important exercises, is discussed in the text. Simple adductor exercises can be used to reduce the risk of injury. (See 'Management of adductor injuries' above and 'Prevention' above.)

ACKNOWLEDGMENTS — The author acknowledges the assistance of the following clinicians in the creation of this topic: Ms. Yolande de Jager, Ms. Samantha Nupen, Ms. Natalie Kalil, Mr. Brett Littlefield, Ms. Bev Roos, and Dr. Brett Woods.