The Gluteus Maximus Muscle
Anatomy and supply
The gluteus maximus muscle builds the most superficial layer of the dorsal gluteal musculature and thus forms the surface anatomy of the gluteal region. Hereby the gluteal fold (or crease) does not represent the lower margin of the muscle but rather results from an arcuate enhancement of the fascia. The innervation is supplied by the inferior gluteal nerve, a branch of the sacral plexus (L4-S2). Numerous vessels and nerves run under the gluteus maximus muscle, including the sciatic nerve, the pudendal nerve and the superior gluteal vessels.
The muscle originates from the sacrum (dorsal part), ilium (behind the posterior gluteal line), the thoracolumbar fascia and the sacrotuberous ligament. Its caudal fibers insert at the gluteal tuberosity of the femur. On the contrary, the cranial fibers go over into the iliotibial tract, a strong fibrous band at the outside of the thigh inserting at the lateral condyle at the tibia.
The gluteus maximus muscle is the most powerful extensor and outward rotator of the hip. Furthermore it supports the stabilization of the hip joint. The contraction of the cranial fibers leads to abduction whereas the contraction of the caudal fibers causes an adduction. The iliotibial tract enhances the lateral thigh fascia and thus relieves the pressure of the femur (tension band principle).
Lesions of the inferior gluteal nerve (e.g. through traumas, hernias or pelvic tumors) may lead to functional deficiency of the gluteus maximus muscle. The affected patients have tremendous difficulties walking up the stairs or standing up from the chair. The standing position itself however is commonly without pathological findings as it is usually compensated by the ischiocrural musculature. Purulent inflammations underneath the gluteus maximus muscle often remain unnoticed and may spread into neighboring structures (sinking abscess). Because of that and the high risk of nerve or vessel injury an intramuscular injection is not to be administered into the gluteus maximus muscle. The choice of injection site should be preferably the gluteus medius muscle.