The gluteus medius one of the three gluteal muscles

Gluteal muscles

The gluteal muscles are the three muscles that make up the buttocks: the gluteus maximus muscle, gluteus medius muscle and gluteus minimus muscle.-The gluteal muscles:...

, is a broad, thick, radiating muscle, situated on the outer surface of the pelvis

Pelvis

In human anatomy, the pelvis is the lower part of the trunk, between the abdomen and the lower limbs .The pelvis includes several structures:...

.

Its posterior third is covered by the gluteus maximus

Gluteus maximus muscle

The gluteus maximus is the largest and most superficial of the three gluteal muscles...

, its anterior two-thirds by the gluteal aponeurosis

Gluteal aponeurosis

The Gluteal aponeurosis is a fibrous membrane, from the fascia lata, that lies between the iliac crest and the superior border of the gluteus maximus. A part of the gluteus medius arises from this membrane....

, which separates it from the superficial fascia

Superficial fascia

Superficial fascia is found in the subcutis in most regions of the body, blending with the reticular layer of the dermis. It is present on the face, over the upper portion of the sternocleidomastoid, at the nape of the neck, and overlying the sternum. It is mainly loose areolar connective tissue...

 and integument.

Relations

A bursa

Bursa (anatomy)

A bursa is a small fluid-filled sac lined by synovial membrane with an inner capillary layer of slimy fluid . It provides a cushion between bones and tendons and/or muscles around a joint. This helps to reduce friction between the bones and allows free movement...

 separates the tendon of the muscle from the surface of the trochanter over which it glides.

Origin and insertion

The gluteus medius muscle starts, or "originates," on the outer surface of the ilium

Ilium (bone)

The ilium is the uppermost and largest bone of the pelvis, and appears in most vertebrates including mammals and birds, but not bony fish. All reptiles have an ilium except snakes, although some snake species have a tiny bone which is considered to be an ilium.The name comes from the Latin ,...

 between the iliac crest

Iliac crest

-External links: - "Superficial muscles of the gluteal region and posterior thigh." - "Anterior Abdominal Wall: Osteology and Surface Anatomy " - "The Back, Posterior View" * *...

 and the posterior gluteal line

Posterior gluteal line

The posterior gluteal line , the shortest of the three gluteal lines, begins at the iliac crest, about 5 cm in front of its posterior extremity; it is at first distinctly marked, but as it passes downward to the upper part of the greater sciatic notch, where it ends, it becomes less distinct, and...

 above, and the anterior gluteal line

Anterior gluteal line

The anterior gluteal line refers to a bone in the human pelvis. It is the longest of the three gluteal lines, begins at the crest, about 4 cm...

 below; the gluteus medius also originates from the gluteal aponeurosis

Gluteal aponeurosis

The Gluteal aponeurosis is a fibrous membrane, from the fascia lata, that lies between the iliac crest and the superior border of the gluteus maximus. A part of the gluteus medius arises from this membrane....

 that covers its outer surface.

The fibers of the muscle converge into a strong flattened tendon

Tendon

A tendon is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments and fasciae as they are all made of collagen except that ligaments join one bone to another bone, and fasciae connect muscles to other...

 that inserts on the lateral surface of the greater trochanter

Greater trochanter

The greater trochanter of the femur is a large, irregular, quadrilateral eminence and a part of the skeletal system.It is directed a little lateralward and backward, and, in the adult, is about 1 cm lower than the head...

. More specifically, the muscle's tendon inserts into an oblique ridge that runs downward and forward on the lateral surface of the greater trochanter.

Action

With the leg in neutral (straightened), the gluteus medius and gluteus minimus function together to pull the thigh away from midline, or "abduct" the thigh. During gait, these two muscles function principally in supporting the body on one leg, in conjunction with the tensor fascia lata, to prevent the pelvis from dropping to the opposite side.

Additionally, with the hip flexed the gluteus medius and minimus externally rotate the thigh. With the hip extended, the gluteus medius and gluteus minimus internally rotate the thigh.

Dysfunction of the gluteus medius or the superior gluteal nerve can potentially be indicated by a positive Trendelenburg's sign

Trendelenburg's sign

Trendelenburg's sign is found in people with weak or paralyzed abductor muscles of the hip, namely gluteus medius and minimus. It is named after the German surgeon Friedrich Trendelenburg....

.

Variations

The posterior border may be more or less closely united to the piriformis

Piriformis muscle

The piriformis is a muscle in the gluteal region of the lower limb. It was first named by Spigelius, a professor from the University of Padua in the 16th century.- Origin and insertion :...

, or some of the fibers end on its tendon.

The posterior fibres of gluteus medius contract to produce hip extension, lateral rotation and abduction. During gait, the posterior fibres help to decelerate internal rotation of the femur at the end of swing phase.