Oblique popliteal ligament

At a glance

English

Oblique popliteal ligament

Latin (TA2)

Ligamentum popliteum obliquum

System

Ligament

Region

Lower limb

Side

Paired, left and right

About the oblique popliteal ligament

This wide, flattened band of fibrous tissue strengthens the back of the knee joint capsule. It is formed as an expansion of the tendon of semimembranosus, one of the hamstrings. Near the back of the medial tibial condyle, where the tendon attaches, part of it turns upwards and laterally and spreads across the capsule; it is one of several insertions of that muscle.

From this origin the ligament crosses the popliteal region obliquely towards the lateral side. It ends on the back of the femur near the lateral condyle and the intercondylar line, blending with the capsule along the articular margins. It is made of separate bundles with gaps between them, and through these gaps pass vessels and nerves. The middle genicular artery and vein and the middle genicular nerve pierce it, as does a genicular twig of the obturator nerve's posterior division.

The ligament helps to floor the popliteal fossa, and the main artery of the fossa rests directly on it, the deepest structure in the fossa. This close contact means the artery can be injured in knee dislocations and is at risk during surgery at the back of the knee.

Functionally it tightens when the knee is fully straight, helping to stop hyperextension, and it limits external rotation of the tibia on the femur. Because semimembranosus pulls on it, the muscle can tense the posterior capsule as the knee moves. Damage to the ligament is part of injuries of the posteromedial corner of the knee and may leave the joint unstable; surgical repair often does better than conservative care. It can be cut during arthroscopic meniscal repair, and a popliteal cyst often emerges near it, between semimembranosus and the medial head of gastrocnemius.

Attachments and function

Attaches from

An expansion of the semimembranosus tendon at the back of the medial tibial condyle.

Attaches to

The back of the femur near the lateral condyle and intercondylar line, blending with the posterior capsule.

Function

Strengthens the posterior capsule, resists hyperextension of the knee and limits external rotation of the tibia.

Nerve supply

The middle genicular nerve and the genicular branch of the obturator nerve pierce it.

Blood supply

The middle genicular artery, which passes through it to the joint.