The inferior gluteal nerve innervates the gluteus maximus. It is the sole nerve supply to this muscle, carrying fibers from spinal roots L5, S1, and S2. No other nerve contributes motor function to the gluteus maximus, which makes the inferior gluteal nerve uniquely important for hip extension and several everyday movements like standing up from a chair or climbing stairs.
Origin and Course of the Inferior Gluteal Nerve
The inferior gluteal nerve arises from the ventral divisions of L5, S1, and S2 within the sacral plexus. From there, it exits the pelvis through the lower part of the greater sciatic foramen, passing below the piriformis muscle. This is a key anatomical landmark: structures that exit below the piriformis are distinguished from those that exit above it, which helps clinicians and students organize the anatomy of the gluteal region.
Once it emerges below the piriformis, the nerve enters the deep surface of the gluteus maximus. It travels alongside the inferior gluteal artery and vein, which together form a neurovascular bundle supplying the muscle. The inferior gluteal artery is a large terminal branch of the internal iliac artery, and it shares a similar path through the greater sciatic foramen before branching into the buttock and posterior thigh.
How It Differs From the Superior Gluteal Nerve
A common source of confusion is the difference between the inferior and superior gluteal nerves. They supply entirely different muscles. The superior gluteal nerve (L4, L5, S1) exits above the piriformis and innervates the gluteus medius, gluteus minimus, and tensor fasciae latae. The inferior gluteal nerve exits below the piriformis and supplies only the gluteus maximus. Remembering the piriformis as a dividing line is one of the most reliable ways to keep these two nerves straight.
What the Gluteus Maximus Does
The movements the inferior gluteal nerve enables are worth understanding, because they explain why damage to this nerve is so functionally significant. The gluteus maximus is the chief extensor of the hip. It powers movements like straightening up from a bent-over position, rising from a seated position, and pushing off while climbing stairs. It is also the main lateral rotator of the hip when the hip is flexed beyond about 25 degrees, and it contributes to hip abduction.
During walking, the gluteus maximus works eccentrically to control the rate at which the hip flexes and to decelerate internal rotation of the lower leg. It is also essential for maintaining an erect posture. Without it, the trunk tends to pitch forward during movement.
What Happens When the Nerve Is Damaged
Because the inferior gluteal nerve is the only nerve supplying the gluteus maximus, injury to it causes a specific and recognizable pattern of weakness. Patients with inferior gluteal nerve damage have difficulty extending the hip against resistance. In practical terms, this means trouble getting out of chairs, climbing stairs, or straightening the trunk after bending forward.
A hallmark sign is the “gluteus maximus lurch.” When the muscle is weak, the body compensates during walking by hyperextending the trunk backward at heel strike. This backward lean substitutes for the missing hip extension force. Over time, the muscle can atrophy, and patients often report pain, weakness, and numbness in the buttock area.
Nerve injury can result from trauma, surgical complications (particularly during hip replacement or procedures in the gluteal region), or entrapment. In entrapment cases, the nerve becomes compressed along its course, producing a combination of deep buttock pain and progressive weakness that worsens with activities requiring hip extension.
Testing Gluteus Maximus Strength
Clinicians can isolate the gluteus maximus from other hip extensors using a simple positioning trick. With the patient lying face down, bending the knee to 90 degrees relaxes the hamstrings and takes them out of the equation. The patient then lifts the thigh off the table while the examiner applies downward resistance just above the knee. If the patient can complete the full range and hold against strong resistance, the nerve and muscle are functioning normally.
With the knee straight, the same test engages all hip extensors, including the hamstrings. So the bent-knee version specifically targets the gluteus maximus and, by extension, evaluates the integrity of the inferior gluteal nerve. A noticeable difference in strength between the two positions points toward gluteus maximus weakness rather than a general hip extensor problem.