Hip and thigh muscles

Iliacus

Iliacus is a large triangular shaped muscle that lies over the surface of the ilium, lateral to the lower part of the psoas major and psoas minor muscles. Its fibers merge with fibers of the psoas major muscle around the level of the inguinal ligament to become the iliopsoas muscle – the main flexor of the thigh. Iliacus receives its innervation from the femoral nerve (L2-L4) and functions to flex the trunk and hip and externally rotate the thigh.

Psoas major

Psoas major is a long, thick, and fusiform muscle that lies lateral to the lumbar vertebrae and medial to quadratus lumborum. At its upper end, it is covered by the medial arcuate ligament as it passes through the diaphragm.

It originates from the T12-L4 vertebrae and descends to insert onto the lesser trochanter of the femur after fusing with the iliacus muscle. Part of the lumbar plexus is embedded into the muscle, with the anterior rami of spinal nerves L1-L3 innervating it. Psoas major flexes and laterally flexes the trunk. It also flexes and laterally rotates the thigh at the hip joint.

Psoas minor

Psoas minor is a long, thin, and fusiform muscle that lies anterior to psoas major. It is variably present, seen only in about 40% of people. Like psoas major, it is innervated by the anterior rami of spinal nerves L1-L3 and has the same function.

Now to solidify your newly acquired knowledge about the iliopsoas group of muscles take a look at the following quiz!

Superficial layer

The gluteus maximus, gluteus medius, gluteus minimus, and tensor fasciae latae muscles are the large and superficial gluteal muscles. They have a variety of functions on the hip joint including extension, external and internal rotation, and abduction and adduction of the thigh at the hip joint.

The tensor fasciae latae is the only muscle of the group to also cross the knee joint, so it acts on the leg as well. The superior gluteal nerve (L4, S1) innervates all of these muscles except for the gluteus maximus which is innervated by the inferior gluteal nerve (L5-S2). 

Gluteus maximus

Gluteus maximus is a quadrangular shaped muscle and is the largest and most superficial muscle of the gluteal group. It covers all other gluteal muscles except for the superior part of the gluteus medius.

Its origin is broad, spanning across the ilium, sacrum, coccyx, thoracolumbar fascia, and sacrotuberous ligament. Muscle fibers extend inferolaterally to insert onto the iliotibial tract and gluteal tuberosity of the femur. It is innervated by the inferior gluteal nerve (L5-S2). Gluteus maximus extends, externally rotates, abducts (via its superior part), and adducts (via its inferior part) the thigh at the hip joint. 

Gluteus medius

Gluteus medius is a fan-shaped muscle which lies deep to the gluteus maximus.

It originates between the anterior and posterior gluteal lines and converges towards the femur with the gluteus minimus muscle to insert on the greater trochanter. Like the gluteus minimus, gluteus medius is innervated by the superior gluteal nerve (L4, S1).

Gluteus medius abducts and internally rotates (via its anterior part) the thigh at the hip joint and stabilizes the pelvis.

Gluteus minimus

Gluteus minimus is also a fan-shaped muscle lying deep to the gluteus medius. It originates between the anterior and inferior gluteal lines and converges inferolaterally with gluteus medius to insert near it on the greater trochanter. Like gluteus medius, gluteus minimus is innervated by the superior gluteal nerve (L4, S1) and has the same function.

Tensor fasciae latae

Tensor fasciae latae is a fusiform shaped muscle and the most anterior of the gluteal muscle group. It originates from the anterior superior iliac spine and the outer lip of the iliac crest. It then descends over part of the gluteus medius and gluteus minimus and the lateral aspect of the thigh to insert onto the iliotibial tract. It is innervated by the superior gluteal nerve like gluteus medius and minimus.

Tensor fasciae latae internally rotates and weakly abducts the thigh at the hip joint, externally rotates, and weakly flexes and extends the leg at the knee joint. It also stabilizes both the hip and knee joints.

Test your knowledge on the superficial gluteal muscles with the following quiz!

Deep layer

Looking at the hip from a posterior aspect, the inner hip muscles can be seen running from the medial features of the pelvis laterally to insert onto the proximal femur. They are partially covered by the inferior part of the gluteus maximus muscle. From superior to inferior, their order can be remembered with the mnemonic; Patched Goods Often Go On Quilts.

• Piriformis
• Gemellus superior
• Obturator internus
• Gemellus inferior
• Obturator externus
• Quadratus femoris

In this view, obturator externus is mostly covered, but can still be seen slightly between gemellus inferior and quadratus femoris. There is no common innervation to this group, however most nerves are named after the muscles they innervate.

There are a lot of muscles of the hip and thigh. Learn their anatomy efficiently and easily using Kenhub's muscle anatomy and reference charts!

Practically all muscles in this group have the same function:

• External rotation of the thigh at the hip joint
• Abduction of the thigh from a flexed hip (excluding quadratus femoris)
• Stabilizes head of femur in acetabulum

Piriformis

Piriformis is a pear-shaped muscle named after its shape from the Latin “pirum” for “pear” and “forma” meaning “shape”. It is the most superior gluteal muscle of the deep layer. Originating from the anterior surface of the sacrum, it passes posteriorly and inferiorly through the greater sciatic foramen to insert onto the greater trochanter. As it runs through the greater sciatic foramen, spaces remain above and below the piriformis – the suprapiriform and infrapiriform foramina.

Superior gluteal vessels and nerves pass above the piriformis through the suprapiriform foramen, while inferior gluteal vessels and nerves pass below the piriformis through the infrapiriform foramen. The piriformis is innervated by the nerve to piriformis (S1-S2).

Gemellus superior

Gemellus superior, together with obturator internus and gemellus inferior, form a three-headed muscle known as the triceps coxae. These muscles are not capable of action individually and converge into a common tendon. Gemellus superior is a small, narrow, and triangular shaped muscle. It lies inferior to the piriformis and superior to the obturator internus.

Gemellus superior originates from the ischial spine and attaches to the greater trochanter via a common tendon with the obturator internus and gemellus inferior. It is innervated by the nerve to obturator internus like the obturator internus muscle.

Obturator internus

Obturator internus is a flat and fan-shaped muscle. It lies between the two gemelli muscles, inferior to gemellus superior and superior to gemellus inferior.

Obturator internus originates from the internal (posterior) obturator membrane and the bony border of the obturator foramen. From there, the muscle curves up and around the ischium at almost 90º before passing through the lesser sciatic foramen and inserting onto the greater trochanter via a common tendon with the gemelli muscles.

It is innervated by the nerve to obturator internus (L5-S1) like gemellus superior. 

Gemellus inferior

Gemellus inferior is a small, narrow, and triangular shaped muscle. It lies inferior to obturator internus and superior to the quadratus muscle. Inferior to the muscle, a sliver of the obturator externus lying anterior to triceps coxae can be seen.

Gemellus inferior originates from the ischial tuberosity and attaches to the greater trochanter via a common tendon with the gemellus superior and obturator internus. It is innervated by the nerve to quadratus femoris like quadratus femoris.

Obturator externus

Obturator externus is triangular and flat. It originates from the external (anterior) obturator membrane and the bony border of the obturator foramen. Its muscle fibers expand posterolaterally below the acetabulum and neck of the femur to insert onto the trochanteric fossa.

Obturator externus externally rotates and helps adduct the thigh at the hip joint. It also stabilizes the head of the femur. Since one of its actions is adduction of the thigh, it is sometimes considered a part of the hip adductors.

Quadratus femoris

Quadratus femoris is a flat and rectangular shaped muscle that is the most inferior gluteal muscle of the deep layer, lying inferior to the gemellus inferior. It originates from the ischial tuberosity and inserts inferolaterally to the intertrochanteric crest of the femur.

Of all the external rotators of the thigh, this is the only muscle which does not abduct the thigh thigh from a flexed hip.

Quadratus femoris is innervated by the nerve to quadratus femoris (L5-S1) like the gemellus inferior.

There is a lot to know about the deep muscles of the gluteal region, and it can be challenging. Use this quiz to deepen your knowledge about these muscles.

Gracilis

Gracilis is the most superficial and medial muscle of the group. It is a long, strap-like muscle which descends from the ischiopubic ramus of the pelvis to the medial surface of the tibial shaft. At its insertion, the tendon of the sartorius muscle lies anterior and the tendon of semitendinosus lies posterior. This combined point of insertion is called the pes anserinus. In order to remember the muscles that comprise the pes anserinus you can use the following mnemonic;

Say Grace Sarah

• Sartorius muscle
• Gracilis muscle
• Semitendinosus muscle

Since the gracilis crosses over both the hip and knee joint, it acts on both joints. At the hip, gracilis flexes and adducts the thigh. At the knee, it flexes the leg and internally rotates it. 

Pectineus

Pectineus is the most superior hip adductor and is flat and quadrangular in shape. From the pectineal line of the pubis, it extends laterally underneath the inguinal ligament to insert onto the pectineal line and linea aspera of the femur. Together with the adductor longus, it forms the floor of the femoral triangle. In addition, its medial margin forms the lateral border of the femoral triangle.

Pectineus flexes, adducts, and rotates the thigh at the hip joint as well as stabilizes the pelvis. Unlike the other muscles in the medial compartment of the thigh, it is innervated by the femoral nerve (L2-L3) instead of the obturator nerve. However, because of natural anatomical variation, it is possible for pectineus to be innervated by the obturator nerve as well.

Adductor longus

Adductor longus is also a flat muscle and fans out when it descends towards the knee joint. It is the most anterior adductor muscle and covers parts of the adductor brevis and magnus which lie posterior.

Adductor longus originates at the anterior body of the pubis and inserts on the medial lip of the linea aspera. Together with the pectineus, it forms the floor of the femoral triangle. Its lateral margin forms the medial border of the femoral triangle. It also contributes to the posterior wall of the adductor canal together with the adductor magnus. Adductor longus flexes, adducts, and externally rotates the thigh at the hip joint and stabilizes the pelvis.

Adductor brevis

Adductor brevis is a triangular shaped muscle that lies posterior to pectineus and adductor longus and anterior to adductor magnus. It originates on the pubis superior to gracilis, and inserts onto the linea aspera of the femur lateral to pectineus and adductor longus.

Near the superior aspect of adductor brevis is the obturator canal through which the obturator artery, vein, and nerve pass from the pelvis to the thigh. After passing through the obturator canal the obturator nerve splits into an anterior and posterior division which travel anterior and posterior to adductor brevis. Adductor brevis adducts, flexes, and externally rotates the thigh at the hip joint and stabilizes the pelvis.

Adductor magnus

Adductor magnus is the largest and most posterior muscle of the medial compartment of the thigh. Like adductor longus and adductor brevis, it is a triangular shaped muscle. From its insertion at the pelvis, it fans out to insert along the femur. There are two parts to the adductor magnus muscle:

• Adductor part – the lateral part which originates from the ischiopubic ramus and inserts from the gluteal tuberosity and along the linea aspera to the medial supracondylar line.
• Ischiocondylar part – the medial part which originates from the ischial tuberosity and inserts onto the adductor tubercle. It is also known as the “hamstring part”.

Between the points of insertion is a large opening for the femoral artery and vein to pass from the adductor canal to the popliteal fossa called the adductor hiatus. It also contributes to the posterior wall of the adductor canal together with the adductor longus.

Learn more about the anatomy of the adductor canal in this video:

The two parts of the adductor magnus are innervated by different nerves. The adductor part is innervated by the obturator nerve (L2-L4) like other hip adductors while the ischiocondylar part is innervated by the tibial nerve after it branches off the sciatic nerve (L4). Like other hip adductors, the adductor magnus flexes and adducts the thigh at the hip joint, and also stabilizes the pelvis. In addition, the adductor part externally rotates the thigh and the ischiocondylar part internally rotates and extends the thigh at the hip joint.

Adductor minimus

Adductor minimus is a small muscle that lies between the quadratus femoris and adductor magnus. It is present in 50% of adults and can be fused with the superior border of adductor magnus. It originates from the inferior pubic ramus and inserts onto the gluteal tuberosity to adduct and externally rotate the thigh at the hip joint.