The oblique popliteal ligament crosses the back of the knee joint. A fibrous band of tissue, this ligament is both broad and flat in shape. It originates as an extension of the semimembranosus muscle's tendon. Nerves and vessels pass through holes between the ligament's fascicule, a cluster of its fibers.
The ligament originates at the tibia, or shinbone, and connects to the femur, or thighbone. It provides an important reinforcing function within the knee, acting as a stabilizing structure for the knee's posterior (back) aspect. It shares this function with the arcuate popliteal ligament. If pulled forward or inward, the ligament assists the tightening of the knee's posterior capsule — the knee joint capsule is the ligament structure surrounding the entire knee.
The oblique popliteal ligament is one of the capsular ligaments. Each member of this group works to provide strength to the fibrous capsule. Capsular ligaments also include the quadriceps tendon, the patellar retinacula, and the tibial collateral ligament.