What is a Posterolateral Corner Injury?
The posterior lateral corner of the knee (PLC) is a complex part of the knee where 10 structures reside. These structures include ligaments and muscle tendons. The structures are there to help prevent the backwards movement of the shin bone.
A PLC injury can occur when any of these ligaments and is often associated with other ligament injuries in the knee such as the ACL and/or PCL.
Diagram of the structures of the posterolateral corner of the knee.
How did I get a PLC Injury?
A PLC injury is commonly initiated by falls, sports trauma and/or motor vehicle accidents. Any injury that may hyperextend, externally rotate, or force the tibia into an inward angle may involve the posterolateral corner of the knee. Some common initiating events include a blow to the front inner corner of the knee when the knee is nearly straight, or oppositely, a blow to the back outer corner of the knee when the knee is bent.
Symptoms of a PLC Injury
Symptoms include, but are not limited to:
- swelling and/or pain in the posterolateral aspect of the knee
- numbness and weakness in the foot as a result of peroneal nerve disruption
- weakness in foot flexion, ankle eversion and/or big toe extension
- instability during weight-bearing when walking or on stairs
How is a PLC Injury Diagnosed?
A thorough examination of both knees can diagnose a PLC injury. The clinician will observe the knee during rest and activities such as walking. They will also palpate different structures of the knee to feel any tenderness or asymmetries. A clinician will then move on to perform several tests to identify any laxity (looseness) and asymmetrical differences between the affected knee and the other knee. Based on the results of the performed tests, the clinician will have a good understanding of the integrity of the structures within the knee.
Imaging such as an MRI is often used to visualize and assess the physical structure of the PLC.
The first-week post-injury should comprise of Rest, Ice, Compression and Elevation (RICE Method) to reduce the swelling of the knee. After that, treatment depends on the severity of the injuries to the PLC and can be understood by the following grade system:
Grade 1: sprain with joint pain and tenderness
Grade 2: partial tear of a ligament
Grade 3: complete tear of a ligament
If it is determined to be a grade 1 or grade 2 injury, conservative treatment through physical therapy is recommended. Physiotherapy would include quad strengthening to help offload the compression on the knee, myofascial release, mobility work to improve knee range of motion, lymphatic massage to stimulate drainage of the lower body lymphatic system, etc. If it is a grade 3 injury, surgical repair is typically necessary.