Gluteus accessorius muscle

The gluteus accessorius muscle is a muscle of the pelvic limb located proximally to the hip joint. It is considered a subdivision of the gluteus medius muscle, and may be more or less merged with it.

Conformation: It consists of a flattened fleshy body covered by an aponeurosis that separates it from the gluteus medius muscle. This aponeurosis serves as an insertion point for a portion of the gluteus medius muscle. It thickens at its ventrocaudal end and continues as a flat tendon.

Origin: Ventral part of the gluteal surface of the wing of ilium.

Insertion: On a ridge on the lateral side of the cranial part of the greater trochanter.

Relations: This muscle covers the wing of the ilium, the deep gluteal muscle, part of the iliac muscle, and the origin of the rectus femoris muscle. It is itself almost entirely covered by the gluteus medius muscle.

Action: Mainly abduction and rotation of the femur. It also assists in the extension action of the gluteus medius muscle.

Vascularization: Cranial gluteal artery and cranial gluteal vein.

Nerve: Cranial gluteal nerve.

Description: The accessory gluteal muscle is located in the proximal part of the pelvic limb. It is part of the gluteal muscle group. It has a special relationship with the gluteus medius muscle, of which it is sometimes considered a subdivision. Depending on the species, they can be more or less difficult to distinguish. It consists of a flat fleshy body originating on the gluteal surface of the wing of the ilium. It is covered by an aponeurosis that gradually thickens toward its ventrocaudal end and extends into a flat tendon that attaches to a crest on the lateral surface of the cranial part of the greater trochanter. This aponeurosis enables distinction from the gluteus medius muscle and serves as an insertion point for some of the fibers of this muscle. The gluteus medius muscle covers the dorsal surface of the gluteus accessorius muscle, while the ventral surface of the accessorius muscle covers the wing of the ilium, the gluteus profundus muscle, part of the iliacus muscle, and the origin of the rectus femoris muscle. Its placement and insertions allow it to achieve abduction and rotation of the femur. It assists the gluteus medius muscle in extending the thigh when these two muscles are activated simultaneously. Its vascularization is provided by the cranial gluteal artery and the cranial gluteal vein. This muscle is innervated by the cranial gluteal nerve.

Variations:

• In equines, its origin on the wing of the ilium is limited dorsally by the single gluteal line. It is closely attached to the gluteus medius muscle near its origin and becomes increasingly easy to separate toward its ventrocaudal end.