If Only I Knew...
Anything About the Popliteus Muscle
By Marie-Catherine Bruno, BScPT, Cped(C).
The popliteus muscle is a fairly small muscle located behind the knee. It runs from the lateral side (outside) of the femur to the medial side of the tibia, lying deep beneath the main calf muscle (gastrocnemius). Its role is to unlock the knee just after the heel touches the ground when you are walking or running, so that you can slightly bend the knee and absorb the impact created while hitting the ground (that moment is called heel strike). It also has an important role when running downhill as it assists the posterior cruciate ligament (commonly known as the PCL) in decelerating the femur and preventing its sliding forward on the tibia from the gravity force.
Like most muscles, when a problem arises it is most likely to target the weakest part of it, meaning the tendon, or one of its attachments to either the bone or the muscle belly. Also, tendons do not benefit of as good of a blood supply as muscle bellies do, so they do not heal as fast when they are damaged. So if we look back at the muscle’s location, the pain is most likely to be felt on the side of the knee where the tendon attaches. Somehow, the medial tendon is usually more symptomatic than the lateral one. In other words, the pain is generally felt on the medial side of the knee. The pain is usually typical of a tendonitis, meaning that in its early stage the pain will start more towards the end of your training session. As it gets more inflamed, you may also start to experience pain first thing in the morning. When you reach the chronic phase, you may have more pain at the beginning of your run from the scar tissue build up, and as your muscles warm up and adhesions break down, the pain slowly subsides.
Because of its role in assisting the PCL on downhills, most runners will start developing symptoms after an abnormally long hill-training session, or after coming down from a hike. That is to say, if you mainly train on flats, you are very unlikely to develop a Popliteus Syndrome.
People with unstable knees (torn ligaments, torn meniscus, arthritis…) are also prone to develop a popliteus problem because of its important role in stabilizing the knee.
The Popliteus Syndrome remains under-diagnosed to this day, meaning that a lot of runners suffer from it without knowing. Its small role in gait function and its deep location make it unsuspected and underestimated by a lot of health professionals. Also its symptoms are strangely very similar to those of a torn Medial Collateral Ligament (MCL) or of a torn meniscus. The only clinical test that seems very reliable remains the Muscle Test where the specialist isolates the popliteus for a contraction under stress. This test usually shows signs of weakness and pain.
So if you have been experiencing pain on the medial side of your knee and it does not seem to heal, ask your health professional about the popliteus.
The Popliteus Syndrome is simply a tendonitis, so it should be treated the same way we treat a tendonitis, meaning rest, anti-inflammatory treatment (either electrotherapy, cryotherapy, or medication… or all of them!) and gentle massages and stretching. As it becomes asymptomatic (no more pain), then strengthening should begin along with deeper massages to break down scar tissue and a gradual return to running. Hills should be avoided until pain has completely disappeared from the running sessions and that the muscle is strong and painfree when tested.
If the cause resides in your knee being unstable (see Causes above), then consult your physical therapist or your personal trainer for deep muscles strengthening and stabilizing exercises, like co-contractions.
The Popliteus Syndrome is fairly easy to treat and responds well to treatment and rest, but the challenge remains in the diagnosis… so keep your eyes open!