portion of the FCL. The short head of the biceps also has 3 important arms in the posterolateral corner. The capsular arm attaches to the posterolateral capsule as well as the fibula, just lateral to the styloid and provides a strong attachment to the capsule, lateral gastrocnemius tendon, and capsuloosseus layer of the IT band. The fabellofibular ligament is actually a thickening of the capsular arm of the biceps femoris as it runs distally to the fibula. The direct arm attaches to the posterior and lateral aspect of the fibular styloid. The anterior arm attaches to the tibia at the same site as the mid-third lateral capsular ligament and is often injured in Segond fractures. Injuries to the biceps femoris tendons have been reported in patients with anterolateral-anteromedial rotatory instability. The popliteus tendon's main attachment is on the femur at the proximal portion of the popliteus sulcus. As the tendon runs posteriorly and distally behind the knee, it gives off 3 fascicles that attach to and stabilize the lateral meniscus. The popliteus tendon provides static and dynamic stabilization to the knee during posterolateral rotation. The iliotibial band (IT band) is mainly divided into two layers, the superficial and capsuloosseus layers. The superficial layer runs along the lateral knee and attaches to Gerdy's tubercle and sends a deeper portion that attaches to the lateral intermuscular septum (IM septum). The capsuloosseus layer extends from the IM septum and merges with the short head of the biceps femoris attaching with it at the anterolateral aspect of the tibia. The IT band stabilizes the posterolateral corner by helping to prevent varus opening. The lateral gastrocnemius tendon inserts on the supracondylar process of the femur slightly posterior to the FCL. Injuries involving this tendon are typically associated with severe traumas and are not often seen. Diagnosis The majority of posterolateral knee injuries occur in combination with another ligamentous injury, such as a cruciate ligament tear. This can make the diagnosis difficult and calls for the use of plain film radiographs and MRI to aid in the diagnosis. During the physical exam, it is imperative to assess a patient for signs of nerve injury as up to 15% of PLC injuries have associated nerve damage. Numbness, tingling, and/or dorsiflexor/great toe extensor muscle weakness all may suggest possible nerve damage. Radiographs Normal antero-posterior (AP) radiographs are useful to look for Segond fractures and fibular head avulsion fractures.