The gluteus maximus is innervated by the inferior gluteal nerve, which carries motor fibers from spinal nerve roots L5, S1, and S2. This nerve is the sole motor supply to the gluteus maximus, meaning damage to it eliminates the muscle’s ability to contract. Understanding this innervation matters for anyone studying anatomy, rehabilitating a hip injury, or trying to make sense of unexplained weakness in hip extension.
The Inferior Gluteal Nerve
The inferior gluteal nerve exits the pelvis through an opening called the greater sciatic foramen, passing underneath the piriformis muscle before splitting into several branches. These branches enter the gluteus maximus on its deep (inner) surface, roughly 5 to 6 centimeters from two bony landmarks: the tip of the greater trochanter (the bony bump on the outer hip) and the posterior superior iliac spine (the bony point you can feel at the top of your pelvis near the low back). The nerve enters the lower third of the muscle belly.
Although textbooks have traditionally described the inferior gluteal nerve as purely motor, more recent dissection studies suggest it often gives off one or two small cutaneous branches in about 75% of people. These supply sensation to a small area of skin over the buttock, but the nerve’s primary role remains powering the gluteus maximus.
Spinal Nerve Roots: L5, S1, and S2
The fibers that form the inferior gluteal nerve originate from three spinal levels in the lower back and sacrum: L5 (the lowest lumbar vertebra), S1, and S2 (the top two sacral segments). These nerve roots merge within the pelvis to form the inferior gluteal nerve before it exits through the greater sciatic foramen. This means that problems at any of these spinal levels, such as a herniated disc compressing the L5 root or sacral fractures disrupting S1 or S2, can weaken the gluteus maximus even though the inferior gluteal nerve itself is intact.
What the Gluteus Maximus Actually Does
Knowing the innervation helps explain what goes wrong when the nerve is damaged, so it’s worth understanding the muscle’s key jobs. The gluteus maximus is the primary extensor of the hip. It powers movements like standing up from a chair, climbing stairs, and thrusting the hips forward during a sprint. It also works with the hamstrings to pull the pelvis backward when you straighten your trunk from a bent-over position.
Beyond extension, it is the main lateral (outward) rotator of the hip, especially when the hip is flexed past about 25 degrees. It also contributes to hip abduction (moving the leg out to the side), controls how fast the hip flexes during walking, and helps decelerate the inward rotation of the shin bone during gait. That last function is important for knee stability: a weak gluteus maximus can contribute to excessive inward knee collapse during running or squatting.
Blood Supply Alongside the Nerve
The inferior gluteal artery travels in close company with the inferior gluteal nerve, and both structures exit the pelvis through the same route beneath the piriformis. This artery is a large terminal branch of the internal iliac artery. It supplies blood to the gluteus maximus, the piriformis, and skin over the buttock and posterior thigh. Surgeons operating in this region need to account for both the nerve and artery running together, since injury to either can compromise the muscle.
What Happens When the Nerve Is Damaged
Because the inferior gluteal nerve is the only motor nerve supplying the gluteus maximus, injury to it causes a distinctive pattern of weakness. The hallmark sign is difficulty extending the hip against resistance. People with inferior gluteal nerve palsy develop a compensatory gait: at heel strike, they shift the weight of their upper body backward to passively lock the hip into extension, since the gluteus maximus can no longer do this actively. This backward trunk lean is sometimes called a “gluteus maximus lurch” and is visible even to an untrained eye once you know what to look for.
Notably, there is typically no numbness accompanying the weakness. The nerve is overwhelmingly motor, so a person with a damaged inferior gluteal nerve will feel the skin over their buttock normally but struggle with activities like rising from a low seat, climbing hills, or running.
Common Causes of Nerve Injury
The inferior gluteal nerve can be injured during hip replacement surgery, particularly through the posterior approach, where the surgeon works through the buttock muscles. A systematic review and meta-analysis of nerve injuries after total hip replacement found a pooled incidence of 0.36% across all nerve types. The risk is highest in patients with developmental hip dysplasia or prior hip surgery, with reported rates ranging from 0.6% to 3.7% in those populations. The strongest predictor of nerve injury was the overall burden of other medical conditions a patient carried going into surgery.
Outside of surgery, the nerve can be compressed by prolonged sitting on hard surfaces (sometimes called “toilet seat neuropathy”), pelvic fractures involving the sacrum, or masses within the pelvis. Deep intramuscular injections into the buttock that are placed too far medially can also damage the nerve, which is one reason the upper outer quadrant of the buttock is the standard injection site.
How Nerve Damage Is Confirmed
If a clinician suspects inferior gluteal nerve injury, the first step is usually a physical exam testing hip extension strength in various positions. Electromyography (EMG), which measures the electrical activity of muscles, can confirm that the gluteus maximus is denervated. During this test, a small needle electrode is inserted into the muscle to look for abnormal electrical patterns that indicate the nerve supply has been disrupted. Imaging such as MRI may be used to identify the location and cause of the compression or damage along the nerve’s path from the sacral spine through the pelvis to the buttock.