From the Research
The piriformis muscle primarily functions as an external rotator of the hip joint when the thigh is extended and as an abductor when the hip is flexed. Located in the gluteal region of the lower limb, it originates from the anterior surface of the sacrum, passes through the greater sciatic foramen, and inserts on the greater trochanter of the femur. When contracted, it rotates the thigh laterally (outward) when standing or walking, helping to stabilize the hip joint during movement. The piriformis also assists in hip abduction (moving the leg away from the midline) particularly when the hip is flexed, such as when walking up stairs. Additionally, it plays an important role in maintaining pelvic stability during single-leg stance and walking.
The muscle's clinical significance relates to piriformis syndrome, where the muscle can compress the sciatic nerve causing buttock pain and sciatica-like symptoms radiating down the leg. This occurs because the sciatic nerve typically passes beneath the piriformis, though in about 17% of people, the nerve passes through the muscle, increasing susceptibility to compression 1. The diagnosis of piriformis syndrome is often based on clinical criteria, as there is no universally accepted diagnostic test, and treatment typically involves conservative management with rehabilitation principles similar to other soft tissue musculoskeletal conditions 1.
Some key points about the piriformis muscle and its function include:
- It is part of the hip external rotator muscle group 2.
- It plays a role in rotation of the femur upon hip extension and abduction of the femur during flexion of the hip joint 2.
- Variations in the anatomy of the piriformis muscle, such as a three-headed piriformis, can have clinical significance in relation to piriformis syndrome 2.
- The muscle's function and activation patterns have been studied using electromyography, showing activation during exercises involving hip abduction and external rotation 3.
Overall, understanding the function and clinical significance of the piriformis muscle is important for diagnosing and managing conditions such as piriformis syndrome, and for developing effective rehabilitation strategies for patients with hip and pelvic disorders 1.