ischiadicus

Ischiadicus, or nervus ischiadicus in Latin, is the sciatic nerve, the largest nerve in the human body. It arises from the lumbosacral plexus, typically receiving fibers from L4 to S3. The nerve exits the pelvis through the greater sciatic foramen, usually inferior to the piriformis muscle, and runs down the posterior thigh beneath the gluteal and thigh muscles. In the mid-thigh it is typically a single nerve, but near the popliteal fossa it divides into two terminal branches: the tibial nerve and the common fibular (peroneal) nerve. Variations in the level and pattern of division are common.

Motor and sensory distribution: The sciatic nerve provides motor innervation to most of the hamstring muscles in the posterior thigh and, via its tibial portion, to the muscles of the posterior compartment of the leg and the plantar muscles of the foot. The common fibular portion supplies the muscles of the anterior and lateral compartments of the leg and contributes to foot and toe movements. Sensory fibers from the sciatic nerve reach the skin of the posterior thigh, most of the leg and foot, and parts of the foot through its tibial and common fibular branches, including the sural nerve contributions to the distal leg.

Clinical significance: The term sciatica describes pain radiating along the sciatic nerve distribution, often due to nerve root compression from a lumbar disc herniation or spinal stenosis, but also from piriformis syndrome or trauma to the nerve. Injury to the sciatic nerve can weaken knee flexion and impair movements of the ankle and foot. Variations in branching patterns can affect the presentation of injuries and surgical approaches.