Distal semimembranosus complex

The distal semimembranosus complex refers to the intricate tendonligamentous structure formed by the multiple distal insertional arms of the semimembranosus tendon and their interrelationship with the posterior oblique ligament at the posteromedial aspect of the knee.

The distal semimembranosus tendon divides into multiple tendinous extensions (arms) as it approaches its insertion. The key components described in the literature include:

• Direct arm inserts onto the posteromedial tibia, just below the articular surface

• Anterior arm wraps anteriorly around the medial tibial condyle, deep to the medial collateral ligament

• Capsular arm extends into the posterior joint capsule behind the posterior horn of the medial meniscus. There is no clear distinction with the meniscal arm of of distal semimembranosus complex

• Meniscal arm a branch that inserts near or behind the posterior horn of the medial meniscus

• Inferior (distal tibial) expansion forms a fascial layer (popliteus aponeurosis) over the popliteus muscle

• Oblique popliteal ligament extension a lateral expansion that forms the largest posterior knee structure, creating a broad fascial sheath over the posterior knee.