![]() Symptoms include mid-buttock pain that radiates down the leg, most often unilaterally. These include piriformis syndrome, trauma, post-operative complications, gynecologic conditions, and herpes zoster. There are also many non-spinal causes or sciatica, which are less common. Other common causes include spinal stenosis, degenerative disc disease, and spondylolisthesis. The vast majority of cases have a spinal cause, such as disc herniation or rupture causing impingement of L5 or S1 nerve roots. Sciatica is defined as irritation or compression of the sciatic nerve that causes pain in the buttock area with radiation to the lower leg. The medial and lateral sural nerves are made up of collateral branches from both the tibial and common peroneal nerves and provide sensation to the calf and a small lateral portion of the foot. The deep peroneal nerve is responsible for sensation in between the first and second toes. The superficial peroneal nerve provides sensory innervation to the lateral leg and dorsum of the foot. The common peroneal nerve further divides into the superficial peroneal nerve and deep peroneal nerve. The sciatic nerve also provides sensory innervation to the skin of the foot and the lower leg (except for the medial leg which is innervated by the saphenous nerve). The tibial nerve further divides into the medial and lateral plantar nerves, which are responsible for the sensation of the sole. The lateral compartment includes peroneus longus and brevis, which are responsible for foot eversion. These muscles are primarily responsible for dorsiflexion of the foot and extension of toes. The anterior compartment includes tibialis anterior, extensor hallucis longus, extensor digitorum longus, and peroneus tertius. The common peroneal nerve innervates the anterior and lateral compartments of the leg and foot. These muscles are primarily responsible for plantarflexion and flexion of the toes. The tibial nerve innervates the posterior compartment of the leg and foot which includes the gastrocnemius, soleus, plantaris, popliteus, flexor hallucis longus, flexor digitorum longus, and tibialis posterior. This includes the biceps femoris, semimembranosus, semitendinosus, and the ischial portion of the adductor magnus which allow for knee flexion and hip adduction. The sciatic nerve provides motor innervation to the posterior compartment of the thigh. ![]() The other branch is the common peroneal nerve, which travels down the lateral and anterior compartment of the leg and foot. One branch is the tibial nerve, which continues to descend in the posterior compartment of leg and foot. The sciatic nerve then progresses down the posterior compartment of the thigh deep to the long head of the biceps femoris muscle, superficial to adductor magnus and short head of biceps femoris muscle, and laterally to semitendinosus and semimembranosus muscles. Just before reaching the popliteal fossa, it divides into 2 important branches. It exits the pelvis through the greater sciatic foramen inferior to the piriformis muscle along with the pudendal nerve and vessels, inferior gluteal nerve and vessels, nerve to obturator internus, and posterior cutaneous nerve. ![]() After leaving the lower vertebrae, the nerve fibers converge to form a single nerve. The nerve originates from the ventral rami of spinal nerves L4 through S3 and contains fibers from both the posterior and anterior divisions of the lumbosacral plexus. ![]() The sciatic nerve innervates a significant portion of the skin and muscles of the thigh, leg, and foot. The sciatic nerve is the largest nerve in humans, originating in the lower back and traveling posteriorly through the lower limb as far down as the heel of the foot. ![]()
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