piriformis

The piriformis muscle is located partly inside and partly outside the pelvis. It is generally made up of three or more bellies that originate from the anterior aspect of the sacrum, laterally with respect to the anterior sacral foramina and from the margin of the large ischial incisura.

Its fibers are directed obliquely downwards through the large ischial foramen and by inserting with a single tendon on the inside of the apex of the great trochanter. In an upright position it works as an external rotator (extra rotator), as an abductor and participates in the retroversion of the pelvis (a fixed insertion on the femur moves the base of the sacrum forward and the apex backwards with respect to the iliac wings) and stabilization of the hip.

In the support phase, when the lower limb is subjected to loading, the piriformis contracts to counteract the abrupt internal rotation of the femur. Although there is a great deal of individual variability, the piriformis always takes contact with the sciatic nerve, the largest nerve in the human body that innervates the main muscles of the thigh, hip and knee.

A hypertrophy of the piriformis muscle and / or its inflammation due to repeated or sudden overloads causes in many cases a compression of the sciatic nerve. This compression causes the appearance of the so-called piriformis syndrome, which can trigger severe pain and paraesthesia (tingling) in the gluteal region, the thigh and the leg. In these cases it is possible to get relief from exercises of