Piriformis Muscle

Description

Arising from the anterior (pelvic) surface of the sacrum, the piriformis courses laterally and inferiorly through the greater sciatic foramen to insert on the superior border of the greater trochanter of the femur. Posteriorly, the muscle sits deep to gluteus maximus and posterior to the hip joint capsule, with the acetabulum and femoral head positioned anteromedial to its tendon as it approaches the proximal femur. The iliac crest and acetabulum anchor the regional bony anatomy, and the lower lumbar vertebrae and lumbosacral junction appear superior to the muscle’s sacral origin. A deep external rotator. This relationship matters because the piriformis is a consistent landmark for the greater sciatic foramen and the structures that traverse it, most famously the sciatic nerve, which usually exits the pelvis inferior to the muscle but can pierce it or divide around it in common anatomical variants. Clinically, piriformis hypertrophy or spasm can reproduce sciatica-like buttock pain and posterior thigh symptoms, and the muscle’s proximity to the posterior hip makes it relevant during posterior approaches to the hip and when planning safe trajectories for deep gluteal injections. Small differences in tendon path at the greater trochanter also help explain why hip flexion changes the piriformis from an external rotator to an abductor. Use this plate for teaching deep gluteal anatomy in gross anatomy, kinesiology, and physical therapy curricula, or for illustrating discussions of deep gluteal syndrome, posterior hip pain differentials, and image-guided injection targets in clinical education materials. Anatomical accuracy verified by SciePro's Medical Advisory Board.