Knee
Posterolateral Corner (PLC) Injuries
What is a posterolateral corner injury (PLC)?
The posterolateral corner of the knee, once known as “the dark side of the knee” because doctors did not have a clear understanding of the anatomy and biomechanics, is now a well-recognized cause of knee disability and dysfunction. There are three primary structures that comprise the posterolateral corner of the knee: the LCL, the popliteus tendon, and the popliteofibular ligament. All these structures work together to stabilize the outside of the knee. The LCL is like a tight rope that prevents your knee from gapping open on the outside of the knee. The popliteus tendon and the popliteofibular ligament prevent the tibia (shinbone) from externally rotating (outwards) on the femur (thigh bone).
What causes a posterolateral corner injury?
PLC injuries can occur in several ways including contact (i.e. hit/blow to the inside of your leg, car accident, pivoting injury) or noncontact injuries (falling on a hyperextended knee). Athletes are particularly at high risk, especially those involved in contact sports like football, soccer, and skiing, due to the sudden, forceful impacts and quick direction changes typical in these activities. These injuries allow the outside of the knee to gap open (varus gapping), as well as the increased external (outside) rotation of the lower leg (tibia).
Sometimes, the nerve that is very close to all these structures (the common peroneal nerve) can be affected. This is a highly debilitating injury that needs to be assessed as soon as possible by an experienced surgeon. This injury can sometimes lead to a foot drop (you cannot lift your foot/toes up towards the ceiling) because the nerve is damaged. Sometimes, the nerve can be decompressed restoring full function. Sometimes it is permanently damaged, and a tendon transfer (transferring a tendon from another part of the knee) can be done to help with the foot drop in order to make walking easier.
What are the symptoms of a PLC injury?
- Pain: Pain on the outer side of the knee is a common symptom of a torn LCL or PLC. The pain may range from mild to severe, depending on the extent of the injury.
- Swelling
- Stiffness: The knee may become stiff, making it difficult to fully bend or straighten the leg.
- Instability: An individual with a torn PLC may feel that the knee is unstable, as if it’s “giving way” or unable to support their weight properly, especially when shifting side-to-side. As it is important for rotational stability, patients may be very symptomatic due to instability.
- Movement: Difficulty stopping and cutting towards the affected side.
- Bruising: Bruising can develop around the site of the LCL tear, and the discoloration is often seen on the outer side of the knee.
- Difficulty Walking: Walking may be uncomfortable or painful, particularly if the LCL tear is severe or involving the entire PLC.
- Popping or Clicking Sensation: Some people report a popping or clicking sensation when the injury occurs, which may be followed by pain and swelling.
How is a PLC injury diagnosed?
A combination of a comprehensive physical examination, special x-rays, and an MRI are usually very accurate. Dr. Bryan Penalosa and his team will perform a physical exam that will include testing your knee in an extended (straight) and flexed position to determine the location and severity of the injury. A special x-ray, called a varus stress x-ray, will likely be obtained. This special x-ray allows Dr. Bryan Penalosa to objectively quantify and diagnose (based on validated systems) a posteromedial corner injury with millimeter accuracy. An MRI will allow Dr. Bryan Penalosa to further evaluate the extent of the PLC injury as well as to evaluate the knee for any concomitant ligament, meniscal, or cartilage injuries.
Posterolateral Corner (PLC) Injuries Treatment Options
Can a PLC injury be treated without surgery?
Most of the time injuries to the PLC do not heal on their own because the thighbone and the shinbone (lateral femoral condyle of the femur and lateral tibial plateau of the tibia) are both convex (round) which makes this part of the knee inherently unstable if the ligaments and tendons are damaged. Thus, these injuries should be seen and treated quickly to achieve the best outcomes. Additionally, almost all complete PLC injuries occur with injuries to other knee ligaments (almost 80%). When additional ligaments are involved, surgical reconstruction is required to restore the anatomy.
What are the surgical options for an PLC injury?
Dr. Bryan Penalosa helped to establish a global consensus on the treatment of PLC injuries. Surgeons from around the world agreed that Grade 1 and 2 tears can be treated nonoperatively with physical therapy, while Grade 3 tears should almost always be treated with surgery.
When there is a complete tear of the LCL, or when all the structures of the posterolateral corner of the knee are injured, surgery should be pursued within the first two weeks after injury, and once range of motion has been recovered. This is the best time to repair the structures, before there is significant scar formation, or the tissues become weakened. The position and alignment of the knee can also be anatomically restored during that time frame, rather than delaying and allowing the knee to heal in an abnormal position.
Recent reconstruction techniques have allowed many patients to get back to high-level activities. This was not true in the past when a PLC injury would typically end further sports participation or even limit participation in normal activities because of ongoing knee problems.
Restoring the native anatomy of the posterolateral corner can allow for early postoperative range of motion and produce better outcomes. Using grafts, Dr. Bryan Penalosa performs a technique that reconstructs the injured ligaments to restore all the native insertions of the posterolateral corner. These grafts are typically allografts (from a donor) and are fixated using non-metal screws.
If you wait six weeks or longer to be treated and you are bowlegged (most men are slightly bow-legged), an osteotomy, or a surgical correction of the bow-leggedness, may be needed before proceeding with the ligament reconstruction, to make sure that the surgically reconstructed ligaments do not stretch out due to persistent varus stress on the knee.
Recovering from Posterolateral Corner (PLC) Surgery
Depending on the severity of the PLC injury and the associated ligaments injured, recovery following PLC surgery can take between 9 and 12 months. Physical therapy starts on postoperative day 1 or 2 to work on range of motion. Patients should not bear weight on the operative side for the first six weeks after surgery. Driving on the operative knee is usually allowed at about seven to eight weeks postoperatively. Endurance and strengthening can be started in the second phase of the rehabilitation. Agility exercises start at 4 months post-op, along with the running progression if previous stages have been successfully achieved. Return to sport following an LCL surgery is typically at 9 months post-op.