Proximal tendon of semimembranosus

The proximal tendon of the semimembranosus muscle originates from the anterolateral aspect of the ischial tuberosity as a broad, crescent-shaped footprint that is anatomically distinct from the conjoined tendon of the semitendinosus and long head of the biceps femoris, which attach more posterolaterally.

The semimembranosus tendon is wider than the conjoined tendon, with a mean footprint width of approximately 4.2 cm and a length of about 4.5 cm, and its attachment lies directly anterior to the conjoined tendon footprint.

The proximal tendon itself is notably long, averaging over 30 cm in length, and forms an expansive musculotendinous junction, which is a common site for strain injuries. The tendon is composed of dense connective tissue and is closely related to the sacrotuberous ligament, with some accessory tendinous extensions forming a distinct anteromedial footprint. The semimembranosus muscle belly transitions into the tendon at a considerable distance distal to its origin, contributing to a large muscle-tendon interface area.