Copyright 2009
Author John Udall MD
Introduction
The knee is supplied by two predominant groups of nerves which give rise to the muscular as well as cutaneous innervation of the knee. The posterior group includes the posterior articular branch of the tibial nerve and obturator nerves. The anterior group includes the articular branches of the femoral, common peroneal and saphenous nerves
The obturator nerve arises from lumbar nerve roots (L2,3,4). It supplies the adductor thigh muscles on the inner side of the thigh and its anterior branch which is close to the hip joint sends fibers to the knee. This nerve can cause a referred pain type pattern where a patient with hip pathology presents with knee pain which can fool the examiner.
The femoral nerve arises from lumbar nerve roots (L2,3,4). It enters the thigh passing under the inguinal ligament and supplies the quadriceps muscles as well as the knee joint. The saphenous nerve is a terminal branch of the femoral nerve which runs down the inner aspect of the leg into the foot.
The sciatic nerve is derived from the sacral plexus (L4,5, S1,2,3) and is made up of the tibial (medial) and common peroneal (lateral) nerves contained within a common connective tissue sheath. The sciatic nerve enters the thigh posteriorily and travels down the back of the thigh. It splits into the tibial and common peroneal nerve above the knee. The tibial nerve supplies the superficial and deep hamstring muscles as well as the muscles of the posterior compartment of the leg including the gastrocnemius and soleus muscles. The common peroneal nerve supplies the anterior and lateral compartments of the leg including the peroneal muscles. While the short head of the biceps femoris is supplied by the peroneal branch of the sciatic nerve, the long head of the biceps femoris is supplied by the tibial branch.
The tibial nerve is the larger of the two divisions of the sciatic nerve. It runs vertically through the popliteal fossa directly underneath the fascia and is the most superficial of the neurovascular structures behind the knee. The common peroneal nerve separates from the tibial portion of the sciatic nerve at the apex of the popliteal fossa and then follows the tendon of the biceps femoris along the upper lateral margin of the popliteal fossa to the back of the head of the fibula. The nerve then winds round the neck of the fibula and passes deep to the peroneus longus muscles and divides into the superficial and deep peroneal nerves.
References
Web References
http://www.thekneedoc.co.uk/content.asp?article=32§ion=10
University of Arkansas – Nerve Tables