The popliteal fossa generally describes the diamond-shaped depression on the posterior knee where the distal thigh joins the proximal leg. The somewhat domed roof of the popliteal fossa is formed by the popliteal fascia, a structure that is continuous with the fascia lata superiorly and fascia cruris inferiorly. The distal femur, proximal tibia, and tibiofemoral joint capsule combine with the popliteus muscle to form the floor. Several muscles form the borders of the popliteal fossa with the semimembranosis and semitendinosis tendons superior and medial, the biceps femoris tendon superior and lateral, and the two heads of gastrocnemius inferior.
The popliteal fossa serves as a passageway for several important neurological and vascular structures that travel from the thigh to the leg. This includes two branches of the sciatic nerve—the tibial nerve, and common fibular nerve (also called the peroneal nerve).
The tibial nerve runs centrally through the fossa and then extends inferiorly to the ankle and medially oriented tarsal tunnel. It provides innervation to the gastrocnemius, soleus, plantaris, popliteus, flexor digitorum longus, and flexor hallucis longis muscles, and sensation to the posterolateral leg and lateral portion and sole of the foot.
The common fibular nerve branches and runs more laterally through the popliteal fossa, around the fibular head, and down the lateral leg. It also has both motor and sensory functions, innervating the short head of the biceps femoris muscle directly, and then the tibialis anterior, extensor hallucis longus, extensor digitorum longus, and tibialis tertius muscles via the deep fibular branch and fibularis longus and fibularis brevis via the superficial branch. The common fibular nerve provides sensation to the lateral leg and dorsum of the foot.
Both the popliteal artery and popliteal vein are located slightly medial to the nerves contained within the popliteal fossa. They run side by side and appear under the medial margin of the semimembranosis muscle. The popliteal artery is a continuation of the femoral artery that spans the popliteal fossa before branching into the anterior and posterior tibial arteries at the inferior border of the popliteus muscle. Much like the cubital fossa of the elbow and femoral triangle of the hip, the popliteal fossa contains lymphatic structures, specifically the superficial and deep popliteal lymph nodes.
Because its architecture is primarily comprised of soft tissue, the structures of the popliteal fossa are less prone to compressive pathologies when compared to the carpal tunnel of the wrist, tarsal tunnel of the foot, and thoracic outlet. However, bodywork practitioners may still need to assess and treat the associated soft tissues for a variety of reasons. Knee hyperextension injuries can compromise the popliteus muscle as well as the hamstring tendons. Scar tissue and adhesions in this area are common following hamstring tendon harvest as part of anterior cruciate ligament replacement surgery. Inflammation from both acute and chronic knee pathologies can lead to a Baker’s cyst, an encapsulated area of swelling in the back of the knee (also called a popliteal cyst). It is important to be aware of the margins and contents of the popliteal fossa when accessing and manipulating these structures as part of treatment.
Popliteal Fossa
Borders
Contents
• Lymphatics: Superficial and deep popliteal lymph nodes
Locating the Popliteus Muscle
Follow the muscle fibers laterally and slightly proximal to the lateral femoral condyle.
Christy Cael is a licensed massage therapist and certified strength and conditioning specialist. Her private practice focuses on injury treatment, biomechanical analysis, craniosacral therapy, and massage for clients with neurological issues. She is the author of Functional Anatomy: Musculoskeletal Anatomy, Kinesiology, and Palpation for Manual Therapists (New York: Jones & Bartlett Learning, 2010; jblearning.com). Contact her at christy_cael@hotmail.com.