The posterolateral corner injuries are caused when execessive physical movements break a special ligament. The posterolateral corner is composed of the popliteus muscle, lateral collateral ligament, the posterolateral capsule, and also the popliteofibular ligament. It provides the necessary support to the knee by assuring structural stability to the knee that resist excessive varus stress, external rotation, and posterior translation of the knee. For the first 30° of flexing the knee the Posterior Cruciate Ligament supports posterolateral corner components.
An injury to this region looks rare but people who are more involved in physical activities such as sportsperson are not unaware of this knee injury. This happens more as a result of blow to the anteromedial when the knee is fully extended. When the posterolateral corner of the knee gets injured the person experiences a varus thrust during the standing position with a pain and the patient is unable to walk. These structures are known to have extra articular and therefore ecchymosis will be present in the region.
A test of knee joint known as posterolateral rotary instability test is done to find out the degree of joint laxity. The athlete or the patient lays back in a flat bed for diagnosis as the position as the examiner holds the lower extremities by the great toes, observing any differences in hyperextension, varus movement, or external tibial rotation.
The laxity of the knee joint is determined by the following test. The athlete is supine with the knee in 30° of flexion and the foot extended over the side of the table. The foot is externally rotated and during the rotation of the leg by the knee the examiner notes down the extent of rotation of the tibial tubercles. If the bilateral comparison results into greater extent of rotation on the affected side then the injury in the knee can be suspected. If the dial test is performed at 90° of flexion and less rotation is seen than at 30° an isolated (no PCL involvement) posterolateral corner injury is suspected. The posterior drawer of the test or sag tests is more provocative for an isolated PCL tear. Anyways, these tests are not always 100% true. The knee pain specialist should keep this fact in mind that these tests don’t provide the actual information always and quite often false negative findings. Due to this, the physical exam should be correlated with other diagnostic imaging tests.
The treatment of this injury intensifies with various with the degree of injury. Mild laxity of the knee joints is treated with bracing and rehabilitation. In some case the total instability caused to the knee is often cured during surgical reconstruction.
