The structure indicated is the gluteus minimus.

The gluteus minimus muscle is one of the muscles of the gluteal region. The muscles in the gluteal region are divided into a superficial and deep group. There are four muscles of the superficial group:

1. Gluteus maximus
2. Gluteus medius
3. Gluteus minimus
4. Tensor fasciae latae

There are 5 muscles in the deep group:

1. Gemellus superior
2. Gemellus inferior
3. Quadratus femoris
4. Piriformis
5. Obturator internus

Origin: Dorsal ilium between inferior and anterior gluteal lines and edge of greater sciatic notch.

Insertion: lateral and superior surfaces of greater trochanter

Action: Hip abduction, hip medial rotation (anterior fibres), hip lateral rotation (posterior fibres)

Innervation: Superior gluteal nerve

Learn more about the anatomy of the gluteal muscles in this tutorial.