The posterolateral corner of the knee is the least described and still controversial region of the knee and thus it has been defined as the `dark region` of the knee. Injury of the posterolateral complex may result in the instability of the knee, unsuccessful results following cruciate ligament repair and chronic knee pains that may be followed by osteoarthritis. The injuries of these structures are usually associated with the injury of the other ligaments of the knee and leads to posterolateral instability, which results in varus, external tibial rotation and posterior tibial translation of the knee. Structures in posterolateral corner are defined in three layers from superficial to deep. The first layer includes the iliotibial tract and the biseps tendon. Lateral patellar retinaculum and lateral head of gastrocnemius are located in the second layer. Third layer includes the structures of the posterolateral corner that are least known and show quite extensive variations. Some researchers assume only these structures in this layer as the structures of the posterolateral corner of the knee. The main structures of this layer are lateral collateral ligament, fabellofibular ligament, tendon of popliteus muscle, popliteo-fibular ligament, meniscotibial ligament and arcuate popliteal ligament. Lateral collateral ligament is the most important stabilizer of the knee against varus force in extension and 30 degree flexion. Popliteus muscle is attached to lateral meniscus by popliteomeniscal fascicles in order to provide the dynamic stabilization of lateral meniscus. Popliteofibular ligament, which provides a tight connection between popliteus and fibula, prevents the varus and external rotation of the knee and the posterior translation of the tibia. With these functions, popliteofibular ligament is an important structure that provides static stabilization in the posterolateral corner of the knee.