Oblique popliteal ligament
The oblique popliteal ligament (posterior ligament) is a broad, flat, fibrous band, on the posterior knee. Structure. The oblique popliteal ligament originates from the adductor tubercle of the medial side of the femur. It is also attached to the upper margin of the intercondyloid fossa and posterior surface of the femur close to the articular margins of the condyles. It crosses the popliteal fossa from medial to lateral. It is attached below to the posterior margin of the head of the tibia. It is one of the five insertions of the semimembranosus muscle. The oblique popliteal ligament  forms part of the floor of the popliteal fossa, and the popliteal artery rests upon it. It is formed of fasciculi separated from one another by apertures for the passage of vessels and nerves. It is pierced by posterior division of the obturator nerve, as well as the middle genicular nerve, the middle genicular artery, and the middle genicular vein. Function. The oblique popliteal ligament reduces rotation around the knee joint. When the knee is in full extension, it prevents valgus deformity. It reduces external rotation of the tibia, and internal rotation of the femur. Clinical significance. The oblique popliteal  ligament may be damaged, causing a valgus deformity. Surgical repair of the ligament often leads to better outcomes than conservative management. The oblique popliteal ligament may be cut during arthroscopic meniscus repair surgery.