Structures of posterolateral corner of the knee

1. Popliteus muscle

2. Popliteofibular ligament

3. Arcuate ligament (medial limb- spans popliteus muscle, Lateral limb - joins lateral joint capsule). Arcuate ligament attaches to the apex of fibula but it is right next (posterior) to another critical structure the popliteofibular ligament.

4. Conjoint tendon (fibular collateral ligament, biseps femoris tendon). The fibular collateral ligament and biceps femoris tendon are attached laterally.

The stability of the posterolateral corner of the knee is provided by capsular and noncapsular structures that function as static and dynamic stabilizers, including the fibular collateral ligament, the popliteus muscle and tendon including its fibular insertion (popliteofibular ligament), and the lateral and posterolateral capsule. In particular, posterolateral corner injuries are frequently seen in combination with posterior cruciate ligament (PCL) injuries.

High-grade posterolateral corner injuries are usually associated with rupture of one or both cruciate ligaments. Importantly, failure to address instability of the posterolateral corner structures increases forces at anterior cruciate ligament (ACL) and PCL graft sites and may ultimately predispose to failure of the cruciate reconstruction.

Posterolateral corner has 3 main stabilizer's

1. LCL (is a subset of LCL complex)

2. Popliteus tendon (musculotendinous unit) - consist of anterior and posterior bundle's. Most injurie's commonly involve the miotendinous junction. In rare cases the rare sesamoid bone is found in the popliteus tendon called cyamella which should not be mistaken for avulsion fracture or fabella. Popliteus musculotendinous complex are composed of posterosuperior (the most important) and anteroinferior fascicles which forms roof and floor of popliteus hiatus. When posterosuperior fassicle is injured the meniscus may twirl and become unstable and the patient may report locking.

3. PFL