The oblique popliteal ligament (posterior ligament) is a broad, flat, fibrous ligament on the posterior knee. It is an extension of the tendon of the semimembranosus muscle.
The posterior knee ligament, also known as the oblique popliteal ligament, is a broad, flat, fibrous structure on the back of the knee. It's an extension of the semimembranosus muscle tendon.