Gluteus Maximus
| |
| Gluteus Maximus | |
|---|---|
| Muscle Type | |
| Origin | Gluteal surface of ilium, lumbar fascia, sacrum, sacrotuberous ligament |
| Insertion | Greater trochanter of the femur and iliotibial tract |
| Action | External rotation and extension of the hip joint, supports the extended knee through the iliotibial tract, chief antigravity muscle in sitting and abduction of the hip |
| Synergists | |
| Antagonists | Iliacus, Psoas Major, Psoas Minor |
| Spinal innervation | L5, S1, S2 |
| Peripheral Innervation | Inferior Gluteal Nerve (L5, S1 and S2 nerve roots) |
| Vasculature | Superior and inferior gluteal arteries |
The gluteus maximus muscle is the largest and most superficial of the three gluteal muscles. During the normal gait, the hamstrings provide most hip extension rather than the gluteus maximus.
As the chief hip extensor, it plays a critical role in standing upright, climbing, and rising from a seated position. It forms the mass of the buttock and contributes significantly to the contour of the hip. The gluteus maximus provides power for hip extension, especially during locomotion and activities like running and jumping
Structure
The gluteus maximus is a large, thick, quadrilateral skeletal muscle forming part of the superficial gluteal group. It has a coarse fascicular architecture, with fibers arranged in parallel bundles separated by fibrous septa.
Origin
It originates on the posterior gluteal surface of the ilium (behind the posterior gluteal line), the dorsal sacrum and coccyx, the thoracolumbar (lumbodorsal) fascia, and the sacrotuberous ligament. The superior fibers also arise from the gluteal aponeurosis over the gluteus medius.
Insertion
The muscle converges into two primary insertions. The upper and superficial fibres inserts on the iliotibial tract of the fascia lata, aiding in knee stabilization. The deeper inferior fibers attach to the gluteal tuberosity on the femur. This dual insertion allows the gluteus maximus to influence both hip and knee mechanics.
Action
As the chief extensor of the hip joint, gluteus maximus powerfully extends the flexed thigh and laterally rotates the femur. It is mostly active during rising motions (standing up, climbing stairs) and explosive lower limb movements. The upper fibers assist in thigh abduction, while the lower fibers contribute to thigh adduction. Additionally, by tightening the iliotibial band, it helps stabilize the knee in extension. Notably, it contracts to support the trunk in erect posture and to prevent forward jackknifing at the hip during gait.
Synergists
During hip extension, the gluteus maximus works synergistically with the hamstrings (biceps femoris – long head, semitendinosus, semimembranosus) and the posterior head of the adductor magnus. In lateral rotation of the hip, it is assisted by the deep lateral rotators (piriformis, obturators, gemelli, quadratus femoris). Its upper fibers functions with gluteus medius and tensor fasciae latae.
Antagonists
The primary antagonists are the strong hip flexors – iliopsoas (iliacus and psoas major) and the tensor fasciae latae (for the extension action). The gluteal muscles (gluteus medius and minimus anterior fibers) also oppose its lateral rotation by producing medial rotation. During hip extension, the rectus femoris (a hip flexor) acts as an antagonist.
Spinal Innervation
The muscle receives fibers predominantly from the L5, S1, and S2 spinal nerve roots
Peripheral Innervation
Innervation is via the inferior gluteal nerve (a branch of the sacral plexus). This nerve enters the deep surface of gluteus maximus and exclusively supplies it. Damage to the inferior gluteal nerve (as in posterior hip dislocations or pelvis fractures) can weaken hip extension.
Vasculature
The gluteus maximus has a rich blood supply mainly from the inferior gluteal artery, and also receives contributions from the superior gluteal artery. Venous drainage corresponds through the inferior gluteal veins into the internal iliac vein. These vessels course deep to the muscle near its origin on the pelvis.
Clinical Application
Gluteus Maximus Lurch: Normally the gluteus maximus contracts at the point of heel strike during gait, arresting hip flexion, and thereby slowing forward motion of the trunk. A weakened gluteus maximus causes a backwards lurch (trunk extension) at heel strike on the weakened side, interrupting the forward motion of the trunk. This compensates for the weakness of hip extension.
Tendinopathy: Overuse of the gluteus maximus (e.g., in weightlifting or hill running) is less common than gluteal medius tendinopathy but can contribute to posterior hip pain. Enthesopathy at the gluteal tuberosity may cause deep localized pain. Treatment includes rest, stretching, and strengthening.
Nerve Entrapment: The superior gluteal nerve nerve is rarely entrapped, but an inferior gluteal neuropathy (e.g., from injections or trauma) leads to difficulty rising from chairs or climbing stairs due to weak hip extension. Injections in the superolateral quadrant of the buttock are preferred to avoid injuring the sciatic and inferior gluteal nerves.
Injection Targets: The gluteus maximus itself can be used as an injection site for intramuscular medications (e.g., gluteal IM injections) but care must be taken to use the upper outer quadrant to avoid the sciatic nerve. Because of its bulk, it is a suitable site for intramuscular injections for its absorption into circulation.
Surgical Landmark: The inferior border of gluteus maximus is used as a surgical landmark in approaches to the hip. During total hip arthroplasty (Thompson approach), it is retracted or partially detached to allow access to the femoral neck. Also, the gluteal fold (formed largely by gluteus maximus) overlies important structures like the ischial tuberosity, informing incisions for ischial bursitis.
