What is the primary muscle responsible for hip extension?

In human anatomy, the muscles of the hip joint are those muscles that cause movement in the hip. Most modern anatomists define 17 of these muscles, although some additional muscles may sometimes be considered. These are often divided into four groups according to their orientation around the hip joint: the gluteal group; the lateral rotator group; the adductor group; and the iliopsoas group.

The muscles of the hip consist of four main groups

Gluteal group

Main article: Gluteal muscles

The gluteal muscles include the gluteus maximus, gluteus medius, gluteus minimus, and tensor fasciae latae. They cover the lateral surface of the ilium. The gluteus maximus, which forms most of the muscle of the buttocks, originates primarily on the ilium and sacrum and inserts on the gluteal tuberosity of the femur as well as the iliotibial tract, a tract of strong fibrous tissue that runs along the lateral thigh to the tibia and fibula. The gluteus medius and gluteus minimus originate anterior to the gluteus maximus on the ilium and both insert on the greater trochanter of the femur. The tensor fasciae latae shares its origin with the gluteus maximus at the ilium and also shares the insertion at the iliotibial tract.

Adductor group

Main article: Adductor muscles of the hip

The adductor brevis, adductor longus, adductor magnus, pectineus, and gracilis make up the adductor group. The adductors all originate on the pubis and insert on the medial, posterior surface of the femur, with the exception of the gracilis which inserts just below the medial condyle of the tibia.

Iliopsoas group

Main article: Iliopsoas

The iliacus and psoas major comprise the iliopsoas group. The psoas major is a large muscle that runs from the bodies and disc of the L1 to L5 vertebrae, joins with the iliacus via its tendon, and connects to the lesser trochanter of the femur. The iliacus originates on the iliac fossa of the ilium. Together these muscles are commonly referred to as the "iliopsoas".

Lateral rotator group

Main article: Lateral rotator group

This group consists of the externus and internus obturators, the piriformis, the superior and inferior gemelli, and the quadratus femoris. These six originate at or below the acetabulum of the ilium and insert on or near the greater trochanter of the femur.

Other hip muscles

Additional muscles, such as the rectus femoris and the sartorius, can cause some movement in the hip joint. However these muscles primarily move the knee, and not generally classified as muscles of the hip.

The hamstring muscles, which originate mostly from the ischial tuberosity inserting on the tibia/fibula, have a large moment assisting with hip extension.

Movements of the hip occur because multiple muscles activate at once. Most muscles are also responsible for more than one type of movement.

Movements of the hip are described in anatomical terminology using anatomical terms of motion. The movement that brings the thighs close to the abdomen is called "flexion". When the legs open, such as in the lotus posture of yoga, this is called "lateral rotation", with the opposite movement called "medial rotation". Hip abduction occurs when the femur moves outward to the side, as in taking the thighs apart. Hip adduction occurs when the femur moves back to the midline. Many muscles contribute to these movements:

• The psoas is the primary hip flexor, assisted by the iliacus. The pectineus, the adductors longus, brevis, and magnus, as well as the tensor fasciae latae are also involved in flexion.
• The gluteus maximus is the main hip extensor, but the inferior portion of the adductor magnus also plays a role.
• The adductor group is responsible for hip adduction.
• Medial rotation is performed by the gluteus medius and gluteus minimus, as well as the tensor fasciae latae and assisted by the adductors brevis and longus and the superior portion of the adductor magnus.
• Each muscle of the lateral rotator group causes lateral rotation of the thigh. These muscles are aided by the gluteus maximus and the inferior portion of the adductor magnus.

Hip muscles also play a role in maintaining the standing posture. These muscles work in an integrated system with muscles of the shoulder, neck, core, lower leg, and supporting muscles of the spine, to provide the ability to stand with good posture.[1] These muscles include the gluteus medius and gluteus minimus which abduct the thigh, prevent swaying of hips, stabilize pelvic region while keeping hips level, and shift an individual’s weight in order to adjust body placement to increase one's overall body stability.[2]

1. ^ "The Muscles Used for Posture". Healthy Living. Retrieved 20 October 2020.
2. ^ "The Role of the Gluteus Medius and Minimus in Hip Stability". paramount-physiotherapy.com. Retrieved 20 October 2020.

• Calais-Germain, Blandine. "Anatomy of Movement", Eastland Press, 1993. ISBN 0-939616-17-3
• Martini, Frederic; Timmons, Michael; McKinnley, Michael. "Human Anatomy", 3rd Edition, Prentice-Hall, 2000. ISBN 0-13-010011-0
• Marieb, Elaine. "Essentials of Human Anatomy and Physiology", 6th Edition. Addison Wesley Longman, 2000. ISBN 0-8053-4940-5
• Netter, Frank H. "Atlas of Human Anatomy", 2nd Edition, Icon Learning Systems, 2001. ISBN 0-914168-81-9

The four main groups of hip muscles are gluteal, adductor, iliopsoas, and lateral rotator, defined by the type of movement they mediate.

Learning Objectives

• Differentiate among the muscles involved in moving the hip joint

Key Points

• The gluteus maximus extends the hip, while the gluteus medius and minimus are involved in hip rotation and abduction (moving hip out from the midline).
• The adductor group (adductor brevis, longus, and magnus along with petineus and gracilis) moves the femur towards the midline from an abducted position.
• The iliopsoas group of muscles (iliacus and psoas major) is responsible for hip flexion.
• The lateral rotator group of muscles (externus and internus obturators, the piriformis, the superior and inferior gemelli, and the quadratus femoris) turns the anterior surface of the femur outward. This motion is aided by the gluteus maximus and the adductor magnus.

• adductor group: The adductor brevis, adductor longus, adductor magnus, pectineus, and gracilis.
• lateral rotator group: The externus and internus obturators, the piriformis, the superior and inferior gemelli, and the quadratus femoris.
• gluteal group: The gluteus maximus, gluteus medius, gluteus minimus, and tensor fasciae latae.
• iliopsoas group: The iliacus and psoas major.

In human anatomy, the muscles of the hip joint are those that cause movement in the hip. Hip joint muscles are divided into four groups according to their orientation and function. Movement at the hip is similar to that of the shoulder joint, but due to increased weight-bearing requirements the range of potential movements is reduced.

Key muscles of the hip: The gluteus maximus can be seen at the top, cut away to expose the underlying muscles.

Muscles in the gluteal group are superficially located and act mainly to abduct and extend the thigh at the hip.

• Gluteus Maximus: The gluteus maximus is the largest of the gluteal muscles and gives structure to the buttocks.
  • Attachments: Originates from the posterior of the pelvis and coccyx (tailbone) and attaches to the femur.
  • Actions: Extends of the thigh and assists with rotation. Is only used when the generation of force is required (e.g. when climbing).
• Gluteus Medius: The fan-shaped gluteus medius muscle lies between the gluteus maximus and minimus and performs a similar function to the gluteus minimus.
  • Attachments: Originates from the posterior of the pelvis and attaches to the femur.
  • Actions: Abducts and medially rotates the thigh and fixes the pelvis during walking.
• Gluteus Minimus: The gluteus minimus is the deepest and smallest of the superficial gluteal muscles and performs a similar function to the gluteus medius.
  • Attachments: Originates from the pelvis and attaches to the femur.
  • Actions: Abducts and medially rotates the thigh and fixes the pelvis during walking.

The muscles of the lateral rotator group are deeply located and as the name suggests, act to laterally rotate the thigh at the hip. All of the lateral rotator group muscles originate from the pelvis and attach to the femur.

• Piriformis: The piriformis is the most superior of the lateral rotator group muscles.
  • Actions: Lateral rotation and abduction of the thigh at the hip.
• Obturator Internus: The obturator internus lines the internal wall of the pelvis.
  • Actions: Lateral rotation and abduction of the thigh at the hip.
• Gemelli: The gemelli are two (superior and inferior) narrow and triangular muscles, separated by the obturator internus tendon.
  • Actions: Lateral rotation and abduction of the thigh at the hip.
• Quadratus Femoris: The quadratus femoris is a flat, square-shaped muscle (actually composed of four distinct muscles). It is the most inferior of the lateral rotator group muscles, located below the gemelli and obturator internus.
  • Actions: Lateral rotation of the thigh at the hip, plays a major role in extension of the lower leg at the knee as well.

(a) Adductor Group Muscles and (b) Key muscles associated with movement at the hip: The deep-lying adductor group muscles originate from the pubis and attach to the length of the femur. The iliacus and psoas major comprise the iliopsoas group and can be seen at the pelvis and lower spine.

The five muscles of the adductor group are responsible for the adduction of the thigh, although several have additional functions.

• Adductor Longus: The adductor longus is a large, flat muscle covering the adductor magnus and adductor brevis.
  • Attachments: Originates from the pubis and broadly attaches to the femur.
  • Actions: Adduction and medial rotation of the thigh.
• Adductor Magnus: The adductor magnus is the largest and most posterior of the adductor group muscles.
  • Attachments: Originates from the pubis and attaches to the femur.
  • Actions: Adducts, flexes, and extends the thigh.
• Adductor Brevis: The adductor brevis is a short muscle lying underneath the adductor longus.
  • Attachments: Originates from the pubis and attaches to the femur.
  • Actions: Adduction of the thigh.
• Obturator Externus: This is one of the smaller muscles of the medial thigh, and it is located most superiorly.
  • Attachments: Originates from the pubis and attaches to the femur.
  • Actions: Laterally rotates the thigh.
• Gracilis: The gracilis is the most superficial and medial of the adductor group muscles. Crossing both the hip and knee joints, it can induce movement at both the hip and knee.
  • Attachments: Originates from the pubis and attaches to the tibia.
  • Actions: Adduction of the thigh at the hip, and flexing of the thigh at the knee.

There are several other muscles that induce movement around the hip joint.

• Psoas Major: The psoas major is located deep in the back near the midline immediately adjacent to the spine. The iliacus and psoas major comprise the iliopsoas group.
  • Attachments: Originates from the base of the spine, combining with the iliacus to attach to the femur.
  • Actions: Flexing of the thigh at the hip joint.
• Iliacus: The iliacus muscle is a large, fan-shaped muscle which lines the interior of the pelvis. The iliacus and psoas major comprise the iliopsoas group.
  • Attachments: Originates from the pelvis and the base of the spine, combining with the psoas major to attach to the femur.
  • Actions: Flexing of the thigh at the hip joint.
• Sartorius: The sartorius is a long thin muscle in the thigh, the longest muscle in the body.
  • Attachments: Originates from the pelvis and attaches to the tibia.
  • Actions: Flexing, abducting and rotation of the thigh at the hip joint.
• Pectineus: The pectineus muscle is a large flat muscle found in the thigh.
  • Attachments: Originates from the pelvis and attaches to the femur.
  • Actions: Adduction and flexing at the thigh at the hip joint.
• Biceps Femoris: A similar muscle to the biceps brachii in the upper arm, also double-headed. Two synergistic muscles are associated with the biceps femoris, the semitendinosus, and the semimembranosus.
  • Attachments: Originates from the pelvis and femur and attaches to the fibula.
  • Actions: Extends and laterally rotates at the hip. The main action is flexing of the lower leg at the knee.

KEY MOVEMENTS

• Extension (bringing thigh behind body) Produced by the gluteus maximus, adductor magnus, and biceps femoris. Flexion (extending thigh to front of body): Produced by the gracilis, psoas major, iliacus, and pectineus.
• Abduction (moving thigh laterally away from pelvis): Produced by the gluteus medius and minimus, obturator externus, gemelli, and sartorius.
• Adduction (returning thigh to midline): Produced by the adductor group of muscles.
• Rotation (rotation of the thigh around the hip joint): Produced by the lateral rotator group of muscles and the biceps femoris, sartorius, and gluteus medius and minimus.