Which nerve passes below the piriformis muscle?

The sciatic nerve is the largest nerve in the body and typically exits the pelvis through the greater sciatic foramen, often passing below the piriformis muscle. This anatomical relationship is important clinically, particularly in cases of sciatica or piriformis syndrome, where compression of the sciatic nerve by the piriformis muscle can lead to pain and neurological symptoms in the posterior hip and lower limb.

The superior gluteal nerve, in contrast, usually emerges above the piriformis muscle, innervating the gluteus medius, gluteus minimus, and tensor fasciae latae muscles. The femoral nerve arises from the lumbar plexus and travels in a different pathway, primarily innervating the anterior compartment of the thigh. The obturator nerve, also stemming from the lumbar plexus, innervates the medial compartment of the thigh and similarly does not traverse beneath the piriformis. Therefore, recognizing the course of the sciatic nerve in relation to the piriformis muscle is crucial for understanding its anatomical and clinical significance.