Location and Function
The oblique popliteal ligament (lig. popliteum obliquum) is located on the posterior aspect of the knee joint (articulatio genus). Biomechanically, this joint functions as a condylar (modified hinge) joint.
This ligament belongs to the group of extracapsular ligaments. It blends directly into the posterior wall of the articular capsule, reinforcing it posteriorly. Together with the arcuate popliteal ligament (lig. popliteum arcuatum), it supports the back of the capsule. The knee joint comprises the articular surfaces of the femoral and tibial condyles, as well as the patella. Inside the joint are two menisci and the intracapsular cruciate ligaments.
Formation of the Oblique Popliteal Ligament
The semimembranosus muscle (m. semimembranosus), which originates from the ischial tuberosity, features a broad, flat tendon. In its distal part, this tendon splits into three bundles:
- Internal (medial) bundle — attaches to the posteromedial surface of the medial tibial condyle.
- Middle bundle — blends into the fascia covering the medial head of the gastrocnemius muscle.
- External (lateral) bundle — extends toward the knee joint capsule and continues as the oblique popliteal ligament (lig. popliteum obliquum).
At the point where these bundles diverge, the semimembranosus bursa (bursa m. semimembranosi) is located. The semimembranosus muscle extends the thigh, flexes the leg, and medially rotates it.
Topography: Contribution to the Popliteal Fossa
The oblique popliteal ligament forms part of the floor of the popliteal fossa (fossa poplitea). This fossa is diamond-shaped. The floor of the popliteal fossa is formed by the following structures:
- Popliteal surface of the femur (facies poplitea).
- Posterior part of the knee joint capsule, into which the oblique popliteal ligament blends; in clinical and topographical anatomy, it is also known as Winslow's ligament.
- Popliteus muscle (m. popliteus), which originates from the lateral femoral condyle.
Adjacent Structures and Clinical Significance
The contents of the popliteal fossa are arranged in a typical pattern from superficial to deep:
- Superficially, the small saphenous vein (v. saphena parva) and the medial sural cutaneous nerve run through the area.
- Deeper lies the tibial nerve (n. tibialis), and lateral and deep to it is the common fibular nerve (n. fibularis communis).
- Lying even deeper is the popliteal vein (v. poplitea).
- The deepest position is occupied by the popliteal artery (a. poplitea).
Popliteal aneurysms and Baker's cysts can compress the tibial nerve or the popliteal vein, causing pain and lower leg edema.