Bursa of piriformis muscle

The bursa of the piriformis muscle (posterior subgluteus medius bursa) is located beneath the tendon of the piriformis muscle posterior to the apex of the great trochanter. The bursa lies on and follows the contour of the insertion of the piriformis tendon. Its superficial surface is in contact with, and often adhered to, the deep surface of the gluteus medius tendon. In daily practice, it is very difficult to differentiate it from the trochanteric bursa of the gluteus medius muscle (anterior subgluteus medius bursa) on MRI.

The piriformis bursa functions to reduce friction between the piriformis tendon and the underlying structures, such as the gluteus medius muscle and the greater trochanter. It is lined with a synovial membrane, which is predominantly areolar in type, providing a smooth surface for the tendon to glide over during muscle contraction and movement.[1-2]