Tenoscopy of the tarsal sheath

The tarsal sheath encloses the tendon of insertion of the lateral digital flexor that comprises of the combined deep and superficial heads of the deep digital flexor. It extends from the musculotendinous junction in the caudal crus to the junction of proximal and middle one-thirds of the plantar metatarsus. Proximally the sheath is voluminous as it is unrestrained by overlying structures. At the level of the tarsocrural joint the two structures are separated only by their synovial and thin fibrous walls. The tarsal flexor retinaculum covers the tarsal sheath from the level of the sustentaculum tali to the tarsometatarsal joint forming the tarsal canal. In the proximal metatarsus the overlying metatarsal fascia is thinner and the sheath again more voluminous. Within the tarsal canal the lateral digital flexor tendon is in intimate contact with the fibrocartilaginous surface of the sustentaculum tali. Throughout the sheath there is a continuous mesotenon that extends from the caudal/plantaromedial surface of the tendon to the sheath wall and when intact, this precludes free passage ...