Arcuate popliteal ligament

At a glance

English

Arcuate popliteal ligament

Latin (TA2)

Ligamentum popliteum arcuatum

System

Ligament

Region

Lower limb

Side

Paired, left and right

About the arcuate popliteal ligament

The arcuate popliteal ligament is a thickening of the fibrous capsule at the posterolateral corner of the knee. It lies outside the joint cavity and is Y-shaped, with its stem below and two limbs spreading upwards. The stem is attached behind the fibular head, close to its apex.

From the stem, the medial limb arches over the popliteus as that muscle's tendon emerges from the joint, and it merges with the posterior capsule and the oblique popliteal band. The lateral limb runs up to the region of the lateral femoral condyle and epicondyle, where it merges with the outer head of gastrocnemius. The arch it forms over the popliteus tendon gives the ligament its name.

Together with the fibular collateral ligament, the popliteofibular ligament and the popliteus tendon, it makes up the posterolateral corner, a group of structures that braces the outer back of the knee. This corner resists varus angulation, external rotation of the tibia and backward displacement of the outer tibial plateau, and it works with the posterior cruciate ligament in these roles.

Injuries to the posterolateral corner are often missed. They usually occur with cruciate tears, after a blow to the front and inner side of an extended knee or a twisting hyperextension. Untreated, they leave the knee rotating outwards too far and can cause a cruciate reconstruction to fail. The dial test, comparing how far each foot turns outwards with the knee bent, is used to detect them, and surgeons often repair or reconstruct these structures together.

Attachments and function

Attaches from

The back of the fibular head, near the apex.

Attaches to

By a medial limb into the oblique popliteal ligament and posterior capsule, and a lateral limb to the lateral femoral condyle region, joining the outer gastrocnemius head.

Function

Reinforces the posterolateral capsule and helps resist varus, external rotation of the tibia and backward displacement of the lateral tibial plateau.

Blood supply

Branches of the inferior lateral genicular artery.