The hip is one of the strongest joints of the human body. This circumstance is due to the variety of muscles that surrounds, stabilizes and moves it. Medical students often have difficulties to properly understand the large number of individual muscles with their structures and functions. It is, therefore, advisable to divide the muscles into groups in order to obtain a better overview that will, in turn, facilitate the learning process. This article is intended to provide the desired overview.
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Image: “Gluteal Muscles that Move the Femur” by Phil Schatz. License: CC BY 4.0


The Flexors of the Hip

Altogether four large muscles constitute the flexor muscle group of the hip joint: these include the iliopsosas, the rectus femoris, the tensor fasciae latae, and the sartorius muscles.

Gluteal Muscles that Move the Femur

Image: “Gluteal Muscles that Move the Femur” by Phil Schatz. License: CC-BY 4.0

There are also some other muscles that assist in the flexion of thigh at the hip joint, but they are not part of the flexor muscle group. These muscles include:

  • Pectineus
  • Adductor longus
  • Adductor brevis
  • Gracilis
  • Gluteus medius
  • Gluteus minimus

Iliopsoas muscle

The iliopsoas muscle is anatomically a combination of two muscles: the psoas major and the iliacus muscles. Both these muscles are separate and distinct at their proximal origin but they combine in the thigh and are distally inserted at the common point, the lesser trochanter of the femur.

Anterior Hip Muscles

Image: “Musculus psoas major” by Beth O’Hara. License: CC BY-SA 3.0

The psoas major is subdivided into a superficial and a deep layer. The superficial layer originates from the 12th thoracic vertebra, the 1st to 4th lumbar vertebrae, and the corresponding intervertebral discs and bodies. The deep layer originates from the processus costalis of 1st to 5th lumbar vertebrae. Their common insertion is the lesser trochanter of the femur. It is innervated by the lumbar plexus at the levels of L1-L3. It is the strongest flexor of the hip because of its large physiological cross-section.

The iliacus muscle originates from the iliac fossa, ala of the sacrum and the articular capsule of the hip joint. It is inserted together with the psoas major on the lesser trochanter of the femur. It is mainly innervated by the femoral nerve (L3-L4) and is important for flexing the thigh at the hip joint.

 

Functional notes: In addition to their function as hip flexors, both psoas major and iliacus can also synergize other movements. The psoas major is able to perform external and internal rotations of the hip joint. It is also able to cause lateral flexion and inclination of the lumbar spine. Additionally, the iliacus performs adduction, internal and external rotations at the hip joint and a forward bend of the torso with bilateral innervation.

Rectus femoris

Rectus femoris muscle

Rectus femoris muscle

The rectus femoris muscle originates from the anterior inferior iliac spine, and the upper edge of the acetabulum, while it inserts into the tibial tuberosity. It is innervated by the femoral nerve (L2-L4) and flexes the hip joint.

Particularities: The tendon already starts a hand’s width cranial from the patella and continues as ligamentum patellae.

Functional notes: In addition to its function as a hip flexor, the rectus femoris also works as an abductor of the hip joint and as an extensor of the knee joint.

Clinical notes: During endoprosthesis, some parts of the capsule-ligament apparatus of the hip joint are removed. This results in cutting off a part of the origin of the rectus femoris, which may lead to the patient having postoperative problems during the contraction of the quadriceps.

Tensor fasciae latae

Musculus tensor fasciae latae

Musculus tensor fasciae latae

The tensor fasciae latae is originated from the anterior superior iliac spine, and it runs together with the gluteus maximus muscle and is inserted into the iliotibial tract. It functions as a flexor at the hip joint and is innervated by the superior gluteal nerve (L4-L5).

Particularities: It is ventral of the gluteus medius muscle and is an evolutionary split of this muscle.

Functional notes: In addition to its primary function, this muscle can perform an abduction and internal rotation of thigh at the hip joint. It is involved in the lateral stabilization of the knee joint because of its connection with the knee joint via the tractus iliotibialis.

Clinical notes: If the lateral fascia is under extreme stress due to an irritation of the tensor fasciae latae muscle, it can lead to a so-called coxa saltans (“snapping hip syndrome”). The result is a snapping sound when the iliotibial tract slips over the major trochanter during flexion and extension of the hip. If the problem is long-lasting, it may also lead to inflammation of the trochanteric bursa which can be very painful.

Sartorius

Musculus sartorius

Musculus sartorius

The sartorius muscle originates from the anterior superior iliac spine and is inserted at the upper medial side of the tibia. It is innervated by the femoral nerve (L2-L3) and it is a flexor of the hip joint.

Particularities: Together with gracilis and semitendinosus muscles, it forms the conjoined tendon “Pes anserinus” (goose feet) at its insertion.

Functional notes: In addition to the flexion, it can also perform an abduction and external rotation in the hip joint and an internal rotation in the knee joint.

The Extensors of the Hip

Flexoren-der-Hüfte-3

Image: “Gluteal Muscles that Move the Femur” by Phil Schatz. License: CC-BY 4.0

The extensor muscle group of the hip joint consists of the gluteus maximus muscle, and the muscles of the ischiocrural muscle group which consists of the biceps femoris, the semitendinosus, and the semimembranosus muscles.

There are also some other muscles that assist in the extension of the hip, but these are not part of the extensor muscle group. These muscles are:

  • Glutaeus medius
  • Glutaeus minimus
  • Adductor magnus
  • Short external rotators (e.g. piriformis, obturators)

Gluteus maximus

gluteus maximus

Image: “Gluteus maximus muscle” by Användare: Chrizz. License: CC BY-SA 3.0

The Gluteus maximus is the largest and most superficial of all the gluteal muscles. It originates from the ilium, sacrum, coccyx and the sacrotuberous ligament. Together with the tensor fasciae latae muscle, some of its fibers are inserted into the iliotibial tract, while remaining fibers are inserted at the gluteal tuberosity. It is innervated by the inferior gluteal nerve (L4-S1) and functions as an extensor of the hip joint.

Particularities: The caudal part of this muscle also goes to the linea aspera.

Functional notes: In addition to its primary function, it is a strong external rotator of the hip. Because of its planar propagation, there are both cranial and caudal fibers present. This allows the performance of abduction and adduction in the hip joint (auto-antagonism). In addition, it centers the caput femoris in the socket.

Clinical notes: If the musculus glutaeus maximus is subjected to pathophysiological pressure for too long, the bursa near the insertion may become inflamed (bursitis).

Biceps femoris

Musculus biceps femoris

Musculus biceps femoris

The first muscle of the ischiocrural group has two heads of origin: long head and short head. Both muscle heads are the extensors of the hip joint.

The long head is originated from the ischial tuberosity, while the short head is originated from the linea aspera and the lateral intermuscular femoral septum. They insert together at the dorsal surface of the head of the fibula.

The long head of biceps femoris is innervated by the tibial nerve (L5-S2), and the short head is innervated by the common fibular nerve (L5-S2). Both these nerves are the divisions of the sciatic nerve.

Functional notes: In addition to its primary function in the hip, it is also a flexor and external rotator of the knee joint.

Clinical notes: Proximal damage to the tibial nerve does not impair the capability to flex the muscle at the knee. This is because of the fact that the small head is innervated by the common fibular nerve and can, therefore, continue its part of movement function.

Semitendinosus

The semitendinosus muscle is originated from the ischial tuberosity and it is inserted at the medial surface of the upper part of the tibia. It extends the hip joint during active innervation by the tibial nerve (L5-S2), which is a division of the sciatic nerve.

Particularities: At its insertion, it forms the conjoined tendon pes anserinus (goose feet) together with the gracilis and the sartorius muscles.

Functional notes: In addition to its primary function in the hip, it also performs a flexion and internal rotation in the knee joint.

Semimembranosus

The semimembranosus muscle is originated from the ischial tuberosity and it is inserted at the medial condyle of the tibia. It is innervated by the tibial nerve (L5-S2), which is a division of the sciatic nerve. It is an extensor at the hip joint.

Functional notes: In addition to its primary function in the hip, it can perform a flexion and internal rotation in the knee joint.

The Abductors of the Hip

Flexoren-der-Hüfte-3

Image: “Gluteal Muscles that Move the Femur” by Phil Schatz. License: CC-BY 4.0

The abductor group of the hip consists of the gluteus medius, gluteus minimus, and piriformis muscles.

Other muscles also assist in the abduction of the thigh at the hip joint, but they do not belong to the abductor group. These include:

  • Tensor fasciae latae
  • Gluteus maximus (cranial fibers)

Gluteus medius

Musculus glutaeus medius

Image: “Posterior Hip Muscles 3″. License: CC BY-SA 3.0

The gluteus medius arises from the ilium bone between the medial and posterior gluteal lines and inserts at the greater (major) trochanter of the femur. It receives its innervation from the superior gluteal nerve (L4-L5) and abducts the hip joint.

Particularities: Its dorsal third is covered by the gluteus maximus muscle and the trochanteric bursa. 

Functional notes: In addition to its primary function, it causes flexion and internal rotation (ventral parts) as well as extension and external rotation (dorsal parts).

Clinical notes: In the case of a weakening of the glutei medius and minimus muscles, the stabilization of the pelvis while walking is no longer guaranteed, and it sinks to the free leg’s side. In medicine, this phenomenon is also called Trendelenburg’s sign.

Gluteus minimus

Musculus glutaeus minimus

Image: “Posterior Hip Muscles 1″. License: CC BY-SA 3.0

The origin of the gluteus minimus muscle is from the ilium bone between middle and inferior lines, and it inserts at the greater trochanter of the femur. It performs abduction in the hip joint during active innervation by the superior gluteal nerve.

Particularities: It is covered by the gluteus medius muscle.

Functional notes: In addition to its primary function, it works synergistically with the gluteus medius muscle for flexion, extension and internal and external rotations at the hip joint.

Trendelenburg’s sign

Trendelenburg’s sign

Clinical notes: In the case of a weakening of the glutei medius and minimus muscles, the stabilization of the pelvis during walking is no longer guaranteed, and it sinks to the free leg’s side. In medicine, this phenomenon is also called Trendelenburg’s sign.

Piriformis

Musculus piriformis

Image: “Posterior Hip Muscles 1″. License: CC BY-SA 3.0

The piriformis muscle originates from the pelvic surface of the sacrum, the sacrotuberous ligament and the socket of the iliosacral joint and inserts at the greater trochanter of the femur. It is innervated by the sacral plexus (S1-S2) and acts as an abductor of the hip joint.

Particularities: There is a gap above the piriformis, the so-called suprapiriform foramen. The superior gluteal nerves and vessels pass through it.

Functional notes: Starting at a hip flexion of 60 degrees, the muscle reverses its function. The course of the muscle changes in proportion to the rotation axis, which causes different biomechanical reactions: In extended position it goes dorsal, which results in an external rotational effect. In flexed position, it goes ventral and, therefore, leads to an internal rotation. Furthermore, in the flexion position of 60 degrees, the piriformis muscle acts as the hip extensor.

Clinical notes: The irritation of the sciatic nerve at the level of the muscle is called piriformis syndrome. This may be caused by space-occupying morphological changes, like muscular hypertension or hematoma. Patients complain of pain and neural radiation in the buttocks and the lower third of the dorsal lower leg. Erroneous diagnosis can quickly lead to mistake this disease for a herniated disc, even though the area of radiation is not identical.

The Adductors of the Hip

Bild: “Gluteal Muscles that Move the Femur” von Phil Schatz. Lizenz: CC BY 4.0

Image: “Gluteal Muscles that Move the Femur” by Phil Schatz. License: CC-BY 4.0

Most of the muscles functioning in the hip joint belong to the adductor group. These include adductor longus, adductor brevisadductor magnus, pectineus and gracilis muscles.

There are other muscles that also assist in adduction of the hip but are not part of the adductor group. These include:

  • Ischiocrural muscle group
  • Gluteus maximus (caudal fibers)
  • Quadratus femoris

Pectineus

The pectineus muscle originates from the pectineal line of the pubis and the pubic tubercle. It inserts at the pectineal line and the linea aspera of the femur and is innervated by the obturator and femoral nerves (L2-L4). It serves as the adductor for the hip joint.

Particularities: Together with the iliopsoas muscle, it forms the iliopectineal fossa, which acts as a pass-through opening of various vessels.

Functional note: An additional function of the pectineus is flexing and external rotation at the hip joint.

Adductor longus

The adductor longus muscle arises from the pubic bone between the pubic crest and symphysis pubis and inserts at the linea aspera of the femur. It is innervated by the obturator nerve (L2-L4) and performs adduction at the hip joint.

Particularities: It borders the entrance of the adductor canal, through which the femoral nerve and vessels pass.

Functional notes: In addition to its primary function, the adductor longus acts as a flexor of the hip until 70 degrees and beyond that as an extensor. Furthermore, it assists in external rotation of the hip.

Gracilis

The gracilis muscle arises from the inferior ramus of the pubic bone and pubic symphysis and inserts at the medial side of the tibial tuberosity. It is innervated by the obturator nerve (L2-L4) and functions as adductor at the hip joint.

Particularities: At its point of insertion, it forms the conjoined tendon “Pes anserinus” together with the sartorius and the semitendinosus muscles.

Functional notes: In addition to its primary function, the muscle also acts as a flexor of the hip until 70 degrees and beyond that as an extensor. Furthermore, it can perform flexion and internal rotation of the knee.

Adductor brevis

The “little short adductor” has its origin in the body and inferior ramus of the pubic bone and its insertion at the linea aspera. During active innervation by the obturator nerve (L2-L4), it acts as an adductor of the hip.

Particularities: Together with the adductor magnus muscle, it forms the deep layer of the hip’s adductors.

Functional notes: In addition to its primary function, it is also a flexor of the hip until 80 degrees. Beyond that, it functions as an extensor.

Adductor magnus

The adductor magnus muscle arises at the inferior ramus of the pubis and the ischial tuberosity and inserts at the linea aspera (proximal part) and at the adductor tubercule (distal part). It gets its innervation from the obturator nerve (L3-L4) and the tibial part of the sciatic nerve (L4-L5). It is a big adductor of the hip joint.

Functional notes: In addition to its primary function, it is a strong extensor of the hip and is also able to perform external rotation (proximal part) and internal rotation (distal part).

The External Rotators of the Hip

The obturator internus, gemelliobturator externus and quadratus femoris muscles form the external rotator group of the hip joint. The piriformis muscle is considered to be part of the group of external rotators in some medical literature, too. Considering the quite extensive external rotatory effect, this is not to be assessed as an error.

There are certain other muscles that assist in external rotation in the hip but are not part of the external rotator group. These are:

  • Gluteus maximus
  • Gluteus medius
  • Gluteus minimus
  • Sartorius
  • Biceps femoris
  • Iliopsoas
  • Adductor magnus
  • Adductor longus
  • Pectineus.

Obturator internus

The obturator internus muscle arises from the obturator membrane and the ischiopubic rami and inserts at the greater trochanter. The innervation is done by the nerve to obturator internus (L5-S2). It performs an external rotation at the hip joint.

Particularities: In some patients, the innervation may additionally vary between the sacral plexus, gluteal nerves, and pudendal nerve.

Functional notes: In addition to its primary function, this muscle is also capable of synergizing adduction and extension, as well as abduction above 90 degrees.

Gemelli muscles

Musculi gemelli

Image: “Posterior Hip Muscles 1″. License: CC BY-SA 3.0

The gemelli muscles consist of superior gemellus  muscle and inferior gemellus muscle.

The superior gemellus muscle arises from the ischial spine, and it inserts at the greater trochanter and obturator internus tendon. It receives its innervation by the nerve to obturator internus (L5-S2) and is an external rotator of the hip joint.

The inferior gemellus muscle arises from the ischial tuberosity and has its insertion at the obturator internus tendon. It is innervated by the nerve to quadratus femoris (L4-S1) and is an external rotator of the hip.

Particularities: In some patients, the innervation may also vary between the sacral plexus, inferior gluteal nerve, and pudendal nerve.

Functional notes: In addition to their primary function, these muscles act as adductors and extensors of the hip from the neutral zero position and can synergize the abduction at a hip flexion of 90 degrees.

Obturator externus

The obturator externus muscle arises from the lateral area of the obturator foramen, the outer surface of the obturator membrane and the ischiopubic ramus. It is inserted at the intertrochanteric fossa of the femur. During active innervation by the nerve to obturatori (L3-L4), it performs an external rotation at the hip joint.

Functional notes: In addition to its primary function, the obturator externus muscle also acts as a weak adductor of the hip. It centers the head of the femur in the socket.

Quadratus femoris

The quadratus femoris muscle arises from the ischial tuberosity and inserts at the intertrochanteric crest of the femur. The innervation is done by the nerve to quadratus femoris (L4-S1), and it is an external rotator of the hip.

Particularities: It may grow together with the inferior gemellus muscle or the adductor magnus muscle. In some patients, this muscle is even entirely missing, without any functional impairment at the hip joint. It can also be innervated by the inferior gluteal nerve and the tibial parts of the sciatic nerve.

Functional notes: The muscle synergizes the extension of the hip joint from flexion and adduction.

The Internal Rotators of the Hip

The actual internal rotator group is not exactly mentioned in the current anatomy literature because there are only a few muscles that perform a purely internal rotation, and their power delivery corresponds to only a third of the external rotators. Muscles that perform an internal rotation at the hip joint are gluteus medius, gluteus minimus, tensor fascia latae and adductor magnus muscles.

A Tabular Overview of the Hip Muscles According to Their Function

Muscle group Muscles with primary function Synergistic muscles
Flexors of the hip joint
  • Iliopsosas
  • Rectus femoris
  • Tensor fasciae latae
  • Pectineus
  • Adductor longus
  • Adductor brevis
  • Gracilis
  • Gluteus medius
  • Gluteus minimus
Extensors of the hip joint
  • Gluteus maximus
  • Biceps femoris
  • Semitendinosus
  • Semimembranosus
  • Gluteus medius
  • Gluteus minimus
  • Adductor magnus
  • Short external rotators
Abductors of the hip joint
  • Gluteus medius
  • Gluteus minimus
  • Piriformis
  • Tensor fasciae latae
  • Gluteus maximus (cranial fibres)
Adductors of the hip joint
  • Pectineus
  • Adductor longus
  • Gracilis
  • Adductor brevis
  • Adductor magnus
  • Ischiocrural muscle group
  • Gluteus maximus (caudal fibres)
  • Quadratus femoris
External rotators of the hip joint
  • Obturatorius internus
  • Gemelli muscles
  • Obturator externus
  • Quadratus femoris
  • Piriformis
  • Glutaus maximus
  • Gluteus medius
  • Gluteus minimus
  • Sartorius
  • Biceps femoris
  • Iliopsoas
  • Adductor magnus
  • Adductor longus
  • Pectineus
Internal rotators of the hip joint (not described separately)
  • Gluteus medius
  • Gluteus minimus
  • Tensor fasciae latae
  • Adductor magnus (distal fibres)

Review Questions

Find the solutions below the references.

1. Which of the following muscles is not among the extensor group of the hip?

  1. Gluteus maximus
  2. Gluteus medius
  3. Biceps femoris
  4. Semitendinosus
  5. Semimembranosus

2. Which of the following muscles has no synergetic function as an internal rotator of the hip?

  1. Gluteus medius
  2. Glutaeus minimus
  3. Tensor fasciae latae
  4. Adductor magnus
  5. Adductor longus

3. Which of the following muscles is responsible for Trendelenburg’s sign?

  1. Gluteus medius + Gluteus minimus
  2. Superior gemellus + Inferior gemellus
  3. Biceps femoris long head + Biceps femoris short head
  4. Adductor longus + Adductor brevis
  5. Obturator externus + Obturatior internus

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