Functional anatomy of the posterolateral structures of the knee.

The major supporting structures of the posterolateral knee were noted to be composed of three components: the fabellofibular ligament, the arcuate ligament, and popliteus muscle with origin from fibular head. We classified this area of the knee into seven major anatomic variants. Popliteus tendon is composed of two parts: the anterior and the posterior fibers. The anterior fibers become tight, while the posterior fibers become lax as the knee was flexed. This phenomenon is more pronounced when the tibia is rotated externally. The midpoint between the anterior and the posterior fibers insertions on the femur appeared to be the isometric point of the popliteus tendon.