Trochanteric bursa of gluteus medius muscle

The gluteus medius (or musculus glutaeus medius), one of the three gluteal muscles, is a broad, thick, radiating muscle. It is situated on the outer surface of the pelvis. Its posterior third is covered by the gluteus maximus, its anterior two-thirds by the gluteal aponeurosis, which separates it from the superficial fascia and integument. (Wikipedia)