Dooley Noted: 7/8/2015
Popliteus is a muscle of the deep crural (leg) compartment. Buried under the enormous bellies of gastrocnemius, this muscle is found beneath its own fascia on the back of the knee. The muscle is located directly superior to the soleal tibial line, where soleus attaches.
Popliteus is innervated by the tibial nerve, like most of the posterior kinetic lower limb chain. This means that low back function – particularly, the lumbosacral plexus – drives the function of this muscle.
Popliteus travels from lateral femoral condyle to medial tibial condyle. Due to its oblique nature, it functions as both a stabilizer and mover. Its depth and joint proximity make it tend more towards dynamic stability of the knee joint. It’s lateral tendon is intracapsular, lending even more to its stabilizing nature and susceptibility to impingement.
Popliteus can laterally rotate a femur if the tibia is fixed, making the muscle a synergist to muscles like the gluteus maximus, psoas, iliacus, sartorius, and the deep hip rotators (PGOGOQ).
If the femur is fixed, the popliteus can internally rotate the tibia. This makes popliteus a synergist to the pes anserine muscles: sartorius, gracilis, and semitendinosus.
Popliteus is also a synergist to sartorius and gracilis in the sagittal plane, assisting in knee flexion. Like other posterior chain muscles, this muscle flexes the knee – but only at initiation. Thus, other knee flexors are dependent upon popliteus for the gait transition from heel strike to suspension.
Popliteus is a one-joint muscle that provides stability. These facts leave the muscle prone to compensating for multi-joint muscles upon their failure to properly execute movement.
In ACL repairs, a posterolateral approach is often utilized by the surgeon, in order to gain access to the ligament. Unfortunately, the lateral popliteal tendon is often cut or damaged, causing the popliteus to concentrically contract (shorten).
This is one of the many reasons why post-surgical ACL knees are difficult to fully extend months after surgery.
Also, the popliteus has a bursa, which is sometimes continuous within the posterior knee joint capsule. This can create posterior knee pain and swelling, as well as movement restriction.
Look for popliteus to disrupt full knee extension, especially in two-joint antagonists like rectus femoris and tensor fascia lata.
Also, look for popliteus to contribute to knee valgus, as it may override important hip stabilizers like gluteus medius.
Don’t forget to look for this muscle to dominate the function of its often two-joint synergists.
As always, it’s your call.
– Dr. Kathy Dooley