Popliteus Is The Problem, Not Baker's Cyst

Back of L leg

I had a patient who came to our clinic this past week complaining of pain in the back of her knee. She looked at her symptoms online and thought she had a Baker's cyst. One look at it and I told her not a chance of it being a Baker's cyst.

After examining her knee carefully, I told her it was her popliteus muscle bothering her.

Here's some background information about my patient. She was about 13 months post ACL (anterior cruciate ligament) surgery, back to weight training, running and training two to three times a week for netball.

Now, as far as I remember, every single patient who've undergone an ACL reconstruction I've treated have had a problem with their popliteus muscle at some point or other.

The popliteus muscle is triangular in shape sitting at the back of the knee. It starts on the lateral femoral condyle (posterior, outer part) of the femur (thigh bone) and the lateral meniscus. It then runs down and across the back of the knee joint to finish on the posteromedial (inner) part of the tibial (shin bone).

R popliteus

The muscle limits excessive internal and external tibial rotation. It helps straighten your knee from full extension by rotating the tibial internally. It also "pulls" the lateral meniscus out of the way during knee bending to prevent too much compressive forces from the femur of the tibial so you don't tear your lateral meniscus.

The poplitues muscle is very seldom the main cause of the problem. There is usually a problem with other stabilizing strutcures in that posterior lateral corner of the knee. It is often hurt because of compensating mechanisms related to that. Such has hip rotator weakness that transmits excessive forces towards the knee. Also, hamstring weakness with hip, knee pivoting movements, which are extremely common in netball.

Consider that most ACL reconstructions for patients now are done usually using the hamstring grafts so the hamstring is consistently weaker thus causing the injury/ strain to the popilteus muscle.

Treating the poplitues muscle for my patient was the easy part. I got her pain free at the end of the session. Ensuring the pain does not come back is trickier.

She needed to address the weakness in her hip stabilizers and hamstrings to prevent the problem from coming back. And that will take some effort on her part.