Injuries to the fibular collateral ligament and posterolateral corner are uncommon, and are usually associated with other ligamentous injuries-in particular, the anterior cruciate ligament and/or posterior cruciate ligament, leading to significant functional impairment. The most common mechanism of injury for this area of the knee involves a combined hyperextension and varus force that is frequently of high energy. As these injuries occur typically in the setting of a multiligament-injured knee, the diagnosis and surgical reconstruction can be extremely challenging. This chapter will discuss the diagnosis of these injuries, including physical examination and imaging techniques, surgical timing, technical considerations, current controversies in management, and postoperative rehabilitation.