Your butt contains far more than the three gluteal muscles most people can name. Beneath the gluteus maximus, medius, and minimus lies a group of six deep rotator muscles, and surrounding them are fascial connections, nerve pathways, and adjacent muscles that together make the buttock one of the most anatomically dense regions in the body. How these muscles work individually and as a unit affects everything from how you walk and run to whether you stay upright as you age.
The Three Gluteal Muscles
The gluteus maximus is the largest muscle in the human body and the most superficial of the buttock muscles, sitting right under the skin and fat layer. Its primary job is hip extension, which means pushing your thigh backward, but it also contributes to external rotation of the leg and helps stabilize the pelvis. Compared to the gluteus maximus of apes and other primates, the human version is distinctively large, and research suggests this enlargement was likely driven by the demands of running rather than walking. During normal, level walking the gluteus maximus does relatively little, but it fires hard during sprinting, climbing, and rising from a seated position.1Europe PMC. The human gluteus maximus and its role in running
The gluteus medius sits underneath the upper portion of the gluteus maximus, fanning out from the outer surface of the pelvis to the top of the thigh bone. Its main role is hip abduction, pulling your leg out to the side, but it is perhaps best known as the primary stabilizer that keeps your pelvis level when you stand on one leg. Every step you take is essentially a brief one-legged stance, and the gluteus medius on the stance-leg side prevents the opposite hip from dropping. When it weakens, people develop a characteristic lurching gait called a Trendelenburg sign.
The gluteus minimus is the smallest and deepest of the three, lying directly beneath the gluteus medius and sharing many of the same attachment points. It assists with hip abduction and internal rotation and works alongside the medius to stabilize the pelvis during movement. Together, the medius and minimus are considered the key hip abductor muscles, though their muscle thickness alone does not reliably predict how strong or functional they are, likely because factors like neural drive and tendon health also play a role.2Europe PMC. Gluteus Medius and Minimus Muscle Structure, Strength, and Function in Healthy Adults: Brief Report
The Deep External Rotators
Buried beneath the gluteal muscles is a group of six smaller muscles collectively known as the short external rotators. These are the piriformis, obturator internus, obturator externus, gemellus superior, gemellus inferior, and quadratus femoris. They run roughly horizontally from the pelvis to the top of the thigh bone and, as a group, function as a single unit that coapts the ball-and-socket joint of the hip, keeping the femoral head seated firmly in its socket.3SpringerLink. The short external rotator muscles of the hip: a cadaveric study on 18 specimens with clinical implications Think of them as the rotator cuff of the hip: individually small, collectively essential for dynamic stability.
Each of these six muscles has slightly different architecture. The obturator internus, for example, has the highest predicted force-generating capacity of the group, while the piriformis has the greatest excursion potential, meaning it can shorten and lengthen through a wider range. In a neutral standing posture, all six are positioned to produce around 91 to 95 percent of their maximum force, which tells you the hip joint evolved for these muscles to work hardest in everyday upright positions.4CrossRef (The FASEB Journal). Deep External Rotator Muscles of the Hip: An Anatomical and Architectural Study
The Piriformis and the Sciatic Nerve
The piriformis deserves its own discussion because of its intimate and sometimes problematic relationship with the sciatic nerve, the longest nerve in the body. In most people, the sciatic nerve exits the pelvis as a single trunk and passes below the piriformis. But in a meaningful minority, the nerve’s anatomy varies. One cadaver study of 56 limbs found that about 7 percent showed atypical arrangements, with the most common variation being the common peroneal branch of the sciatic nerve passing directly through the piriformis while the tibial branch passed below.5PubMed Central. Anatomic Variation of the Sciatic Nerve: A Study on the Prevalence, and Bifurcation Loci in Relation to the Piriformis and Popliteal Fossa
A larger study examining 164 limbs found the rate of this type of variation was substantially higher, around 18 percent, which was a 64 percent increase over the classic 1937 estimates that clinicians still commonly reference. Some of those cases also involved blood vessels or additional nerves running between the sciatic nerve’s branches and the piriformis, adding complexity to what surgeons and therapists encounter.6CrossRef (The FASEB Journal). Novel variations in the anatomical relationship between the piriformis muscle and sciatic nerve: a cadaveric study These anatomical differences matter because when the piriformis muscle spasms, tightens, or swells, it can compress the sciatic nerve and cause deep buttock pain radiating down the leg, a condition often called piriformis syndrome. People with the variant anatomy where the nerve threads through the muscle itself are thought to be more vulnerable to this kind of entrapment.
The Tensor Fasciae Latae and Other Neighbors
Sitting at the front-outer corner of the hip, the tensor fasciae latae is a small muscle that punches above its weight. It merges into the iliotibial band, the thick strip of connective tissue running down the outside of the thigh to the knee. Together, the TFL and the IT band act as a single functional unit that helps stabilize the pelvis during standing, walking, and running, and the TFL works across both the hip and knee joints.7Europe PMC. Isolated pathologies of Tensor Fasciae Latae: Retrospective cohort analysis from a tertiary referral centre
What makes the lateral hip region interesting is how interconnected these muscles are. Both the TFL and the gluteus maximus insert into the iliotibial band, so they share a common attachment point and together cover all the major movements of the hip: flexion, extension, abduction, and rotation.8PubMed Central. The Relationship Between Tensor Fascia Latae and Gluteus Maximus Has the Potential to Indicate Early Intra-articular and Degenerative Pathologies of the Femoral-Acetabular Joint: A Narrative Review Cadaver research has also confirmed that the gluteus medius has a direct adhesion to the IT band along the exposed part of the muscle not covered by the gluteus maximus or TFL, giving the medius a role in controlling IT band tension as well.9PubMed Central. Morphology and Morphometry of the Connection Between the Gluteus Medius and the Midportion of the Iliotibial Band So when people talk about IT band syndrome at the knee, the cause often traces back to how the gluteal muscles and TFL are functioning up at the hip.
Connections to the Trunk and Opposite Side
The gluteus maximus does not just act locally. Through the thoracolumbar fascia, a dense sheet of connective tissue covering the lower back, the gluteus maximus transmits force to the latissimus dorsi in the upper back and even to the lower trapezius near the shoulder blades. This force transfer happens not only on the same side of the body but also crosses over to the opposite side.10CrossRef. Role of Posterior Layer of Thoracolumbar Fascia in Epimuscular Myofascial Force Transmission From Gluteus Maximus to Latissimus Dorsi and Lower Trapezius This is why a strong contraction of one glute can stiffen the entire lower back and why poor gluteal function sometimes shows up as low back pain rather than hip pain. The sacral fibers of the gluteus maximus also contribute to stabilization of the sacroiliac joint, adding yet another way this muscle influences the spine.11Brookbush Institute. Research Review: Gluteus Maximus Stabilization Forces at the Sacroiliac Joint
Nerves Worth Knowing About
The superior gluteal nerve supplies the gluteus medius, gluteus minimus, and tensor fasciae latae. Its branching pattern varies between individuals, but the most common layout is a spray pattern seen in about 70 percent of people. The branch most at risk during hip surgery is the one going to the gluteus minimus, because it passes closest to the greater trochanter, the bony prominence on the outside of the hip where surgeons often work.12PubMed Central. Variability and clinical anatomy of the superior gluteal nerve-A systematic review and meta-analysis Damage to this nerve during hip replacement can lead to lasting weakness in hip abduction and a persistent limp, which is one reason surgeons take careful note of its anatomy preoperatively.
What Happens When These Muscles Weaken
Weak or poorly functioning gluteal muscles show up clinically in several recognizable ways. Greater trochanteric pain syndrome is one of the most common, affecting the lateral hip. It was traditionally blamed on bursitis, inflammation of the fluid-filled sacs that cushion the hip, but current evidence points to tendinopathy of the gluteus medius and minimus tendons as the primary underlying problem. Biomechanical factors like excessive hip adduction and weakness of the abductor muscles increase friction and compression of these tendons against the greater trochanter.13Europe PMC. Greater trochanteric pain syndrome: a review of diagnosis and management in general practice
In older adults, gluteal muscle health has direct implications for fall risk. A study comparing community-dwelling older adults who had fallen with those who had not found that fallers had lower muscle quality and higher fatty infiltration across multiple muscles, but the gluteal muscles were the most affected. Fallers also produced less hip abduction force, and the strongest associations between muscle composition and joint strength were found in the gluteus medius and minimus.14Europe PMC. Gluteal muscle composition differentiates fallers from non-fallers in community dwelling older adults This is consistent with the medius and minimus being the pelvic stabilizers during single-leg stance: when they deteriorate, balance deteriorates with them.
How Hip Shape Influences Gluteal Mechanics
Not everyone’s gluteal muscles work under the same mechanical conditions. A computational modeling study explored how variations in hip bone geometry, specifically the angle of the femoral neck and the width of the pelvis, change the forces that the gluteus medius and minimus must generate during walking. When the neck-shaft angle was steep and the pelvis was narrow, the muscles had shorter moment arms and needed to produce much higher forces to do the same job. The gluteus medius, for instance, had to produce roughly 1,240 newtons in the worst-case geometry compared to about 740 newtons in the most favorable geometry.15BMC Musculoskeletal Disorders. Influence of hip morphology on gluteal muscle biomechanics: a computational modeling study These higher forces mean greater tensile loading on the tendons, which the researchers suggested could create a biomechanical predisposition to gluteal tendinopathy. Because women on average have wider pelvises and different femoral angles than men, these geometric factors help explain why lateral hip pain is more common in certain populations.
Exercises That Target the Glutes
If you are trying to strengthen these muscles, the evidence on which exercises fire the gluteus maximus hardest is fairly clear. A systematic review found that step-ups and their variations produce the highest activation, followed by hip thrusts, deadlifts, lunges, and squats, all of which generated activation above 60 percent of a maximal voluntary contraction.16Europe PMC. Gluteus Maximus Activation during Common Strength and Hypertrophy Exercises: A Systematic Review
For the gluteus medius, the standout exercises look different. Side-plank hip abduction and single-leg squats produce the highest medius activation, with side-plank variations reaching above 80 to 100 percent of maximal voluntary contraction. Front planks with hip extension are unusual in that they strongly activate both the gluteus maximus and the gluteus medius, making them a two-for-one choice.17Europe PMC. Electromyographic analysis of gluteus medius and gluteus maximus during rehabilitation exercises
The gluteus maximus itself is not a uniform slab of muscle. Its upper and lower portions respond differently to different exercises. Movements incorporating hip abduction or external rotation preferentially activate the upper portion compared to the lower portion, while exercises like squats and hip thrusts tend to activate both portions more evenly.18Journal of Orthopaedic & Sports Physical Therapy. Comparison of Electromyographic Activity of the Superior and Inferior Portions of the Gluteus Maximus Muscle During Common Therapeutic Exercises If you have been told to strengthen your glutes and are doing only hip thrusts, you may be underworking the upper fibers that contribute to pelvic stability and abduction.
Gluteal Muscles During Running
Runners depend heavily on their gluteal muscles, but the timing and magnitude of activation change depending on how you run. Research on step rate found that when runners increased their cadence by 10 percent over their preferred rate, gluteus maximus and gluteus medius activity both increased significantly during the late swing phase, the moment just before the foot hits the ground. This pre-activation serves as a braking and stabilizing strategy, preparing the hip to absorb the impact of landing.19Elsevier / Gait & Posture. Changes in Muscle Activation Patterns when Running Step Rate is Increased This finding dovetails with the earlier point about the gluteus maximus being more important for running than walking: as the demands of locomotion increase, the glutes contribute proportionally more.
Muscle Fiber Composition in the Gluteus Maximus
Skeletal muscle contains different fiber types, broadly categorized as slow-twitch fibers that are fatigue-resistant and fast-twitch fibers that generate more force but tire quickly. In the gluteus maximus, the distribution of fast-twitch fiber subtypes does not appear to correlate with age, sex, or grip strength, at least based on biopsy data from patients undergoing hip surgery.20PubMed Central. Differences in Type 2 Fiber Composition in the Vastus Lateralis and Gluteus Maximus of Patients with Hip Fractures This stands in contrast to the quadriceps, where fiber composition changes more predictably with age. The gluteus maximus appears somewhat resistant to the age-related shift in fiber type that other large muscles undergo, though the quality of the tissue, particularly fatty infiltration, still declines with aging as the fall-risk research demonstrates.
What this means practically is that strengthening the glutes in older adults is not primarily about changing fiber types but about maintaining muscle quality, keeping the contractile tissue healthy and limiting the fat that accumulates between and within muscle fibers over time. Programs that load the glutes through a full range of motion and in multiple planes likely do the most to preserve both the structural integrity and the functional capacity of the entire buttock region.