the piriformis: the inferior gluteal nerve also passes backward through the greater sciatic foramen but below the piriformis." Function The major function of the gluteus maximus is to extend the flexed thigh and bring it inline with the trunk. It may prevent the forward momentum of the trunk from producing flexion at the supporting hip during bipedal gait. It is intermittently active in the walking cycle and in climbing stairs and continuously active in strong lateral rotation and abduction of the thigh and also stabilizes the femur on the tibia when the knee extensors are relaxed. In addition to this, the gluteus maximus has an important role during some activities like running or standing up. The gluteus maximus, a large muscle with numerous attachments, is a powerful extensor of the thigh or of the trunk lower limbs are in a fixed position. The gluteus maximus is also a strong hip stabilzer. It extends thigh at the hip, assists in laterally rotating the thigh. It contracts at heel-strike, slowing forward motion of trunk by arresting flexion of the hip and initiating extension. This movement prevents trunk from falling forward. Surprisingly, however, the gluteus maximus is not important posturally, is relaxed when one is standing, and is little used in walking. It is employed in running, climbing, and rising from a sitting or stooped position. It also controls flexion at the hip upon sitting down. Injury From hip replacement Inferior gluteal entrapment neuropathy is rarely reported but is recognized as a complication of the posterior approach to hip arthroplasty. Injuries to the peripheral nerves occur in 0.5% to 8% of patients undergoing total hip replacement. The posterior approach has been assessed most widely and is perhaps the most frequently used, but it is also the one most likely to be associated with damage to the inferior gluteal nerve since this structure is not usually seen. Direct abnormalities of the nerve may be difficult to detect due to the small size of the nerve, although signal intensity alterations in the gluteus maximus may be encountered Diagnostic imaging of peripheral nerves about the hip is a challenging task due to the complex regional anatomy, the small size and intricate course of many nerves. There are also a variety of clinical situations leading to local disturbances in the nerve function the positioning of the inferior gluteal nerve makes it vulnerable to iagtrogenic injury during posterior