The knee is a hinge joint that is responsible for weight-bearing and movement. It consists of bones, meniscus, ligaments, and tendons. The knee is designed to fulfill various amounts of functions, including the following:
- Provide enough stability.
- Help to lower and raise your body.
- Allows twisting of the leg.
- Makes walking much more efficient.
- Supports the body in an upright position without the need for muscles to function.
The posterolateral corner (PLC) is a complex area of tendons and ligaments around the outside of the knee. As a junction of the body, the PLC is something of a ‘meeting point’ for the following…
- Fibular collateral ligament
- Popliteofibular ligament
- Popliteus tendon
- Biceps femoris tendon
- Iliotibial band
The posterolateral corner plays a very important role in stabilizing the knee – if your knee is trying to go into a bowed position (such as changing direction quickly on a ski slope), ligaments tighten and prevent the knee from overextending.
Posterolateral corner injury is a tear of one or more of those tendons and ligaments. It may occur with a twisting injury, a hyperextension injury (knee being pushed too far back past straight), or a blow to the inside or front of the knee. It may also occur with dislocation of the knee when one or more of the other major ligaments (ACL, MCL, or PCL) is also ruptured.
There may also be an injury to the nearby common peroneal nerve, causing weakness and numbness in the leg and foot. Also, depending on the severity and degree of injury, PCL injuries are usually divided into three grades. This classification depends on the degree of joint gapping when the lateral joint is manually stressed along with the end feel when doing this movement. Below are the three grades of a PLC injury:
- Grade 1 PLC injury – Causes minimal instability in the knee with a small, partial tear.
- Grade 2 PLC injury – Partial tear with an endpoint to stressing.
- Grade 3 PLC injury – Complete tear of the ligament with severe instability.