Synovial spaces and sheaths of the hand

This illustration demonstrates the anatomy of the synovial spaces of the hand and the flexor tendon sheaths. The flexor tendons of the hand are enclosed in a double-layered synovial sheath composed of an inner visceral layer and an outer parietal layer, which creates a closed system. There are seven synovial sheaths, including a digital synovial sheath for each of the five digits and a radial and an ulnar bursa extending from the neck of the thumb metacarpal and small finger metacarpal, respectively. The Space of Parona is a potential space between the tendons of the flexor digitorum profundus and the pronator quadratus.