The hip region is located lateral and anterior to the gluteal region, inferior to the iliac crest, and overlying the greater trochanter of the femur.

In adults, three of the bones of the pelvis have fused into the hip bone or acetabulum which forms part of the hip region.

The hip joint, referred to as the acetabulofemoral joint.

The acetabulofemoral joint is between the femur and acetabulum of the pelvis.

The acetabulofemoral joint’s primary function is to support the weight of the body in both standing) and walking or running postures.

The hip has an important role in retaining balance, and for maintaining the pelvic inclination angle.

Hip pain may result from nervous, osteoarthritic, infectious, trauma-related, and genetic reasons.

The greater trochanter is often the only palpable bony structure in the hip region, as the proximal femur is largely covered by muscles.

It is a synovial joint formed by the articulation of the rounded head of the femur and the cup-like acetabulum of the pelvis.

It forms the connection between the bones of the lower limb and the axial skeleton of the trunk and pelvis.

The joint surfaces are covered with a strong but lubricated layer called articular hyaline cartilage.

The cuplike acetabulum forms at the union of three pelvic bones ― the ilium, pubis, and ischium.

The triradiate cartilage is a Y-shaped growth plate that separates the 3 pelvic bones that is fused at ages 14-16.

The acetabulum is a special type of spheroidal or ball and socket joint where the roughly spherical femoral head is largely contained within the acetabulum.

The acetabulum has an average radius of curvature of 2.5 cm.

The acetabulum grasps almost half the femoral ball.

The acetabulum’s a grip is augmented by a ring-shaped fibrocartilaginous lip, the acetabular labrum

The joint space between the femoral head and the superior acetabulum is normally between 2 and 7 mm.

The head of the femur is attached to the shaft by a thin neck region.

The neck of the femur is prone to fracture in the elderly, which is mainly due to the degenerative effects of osteoporosis.

The acetabulum is oriented inferiorly, laterally and anteriorly.

The femoral neck is directed superiorly, medially, and slightly anteriorly.

The transverse angle of the acetabular inlet, Sharp’s angle, and is generally the angle referred to by acetabular angle.

The acetabulum angle can be determined by measuring the angle between a line passing from the superior to the inferior acetabular rim and the horizontal plane.

The acetabulum angle normally measures 51° at birth and 40° in adults, and which affects the acetabular lateral coverage of the femoral head and several other parameters.

The sagittal angle of the acetabular inlet is an angle between a line passing from the anterior to the posterior acetabular rim and the sagittal plane.

The Saginaw angle measures 7° at birth and increases to 17° in adults.

The angle between the longitudinal axes of the femoral neck and shaft, called the caput-collum-diaphyseal angle or CCD angle, normally measures approximately 150° in newborn and 126° in adults.

An abnormally small angle is known as coxa vara.

An abnormally large angle is known as coxa valga.

Coxa valga is often combined with genu varum, bow-leggedness.

Coxa vara leads to genu valgum, known as knock-knees.

An abnormal caput-collum-diaphyseal angle leads to bone trabecular patterns.

Coxa valga leads to more compression trabeculae.

Coxa vara leads to more tension trabeculae.

The fascia lata on the lateral side of hip joint forms the iliotibial tract which functions as a tension band and reduces the bending loads on the femur.

The hip joint capsule of hip joint attaches to the hip bone outside the acetabular lip.

The distance between the femoral head’s cartilaginous rim and the capsular attachment at the base of the femoral neck is constant, which leaves a wider extracapsular part of the neck at the back than at the front.

The hip joint capsule is strong but loose and permits the hip joint to have the second largest range of movement of any joint, and yet support the weight of the body, arms and head.

The hip joint capsule has two sets of fibers: longitudinal and circular.

The circular fibers form a collar around the femoral neck called the zona orbicularis.

The longitudinal retinacular fibers travel along the neck and carry blood vessels.

The hip joint is reinforced by four ligaments.

Three of the reinforcing hip ligaments are extracapsular and one intracapsular.

The extracapsular ligaments are the iliofemoral, ischiofemoral, and pubofemoral ligaments attached to the bones of the pelvis- the ilium, ischium, and pubis respectively.

The extracapsular ligaments of the hip strengthen the capsule and prevent an excessive range of movement in the joint.

The iliofemoral ligament is the strongest ligament in the body, and it prevents the trunk from falling backward without the need for muscular activity in the upright position.

The iliofemoral ligament in the sitting position is relaxed, permitting the pelvis to tilt backward into its sitting position.

The iliofemoral ligament prevents excessive adduction and internal rotation of the hip.

The ischiofemoral ligament prevents internal rotation while the pubofemoral ligament restricts abduction and internal rotation of the hip joint.

The zona orbicularis, a collar around the most narrow part of the femoral neck, is covered by the other ligaments and acts like a buttonhole on the femoral head and assists in maintaining the contact in the joint.

The three ligaments become taut when the joint is extended, stabilizing the joint, and reduces the energy demand of muscles when standing.

The intracapsular ligament, the ligamentum teres, is attached to a depression in the acetabulum and a depression on the femoral head.

The intracapsular ligament is only stretched when the hip is dislocated, and may then prevent further displacement.

The intracapsular ligament is a conduit of a small artery to the head of the femur, the foveal artery.

The foveal artery can become the only blood supply to the bone in the head of the femur when the neck of the femur is fractured or disrupted by injury in childhood.

The foveal artery is a branch of the posterior division of the obturator artery, which becomes important to avoid avascular necrosis of the head of the femur when the blood supply from the medial and lateral circumflex arteries are disrupted.

The blood supply to the hip is from the medial circumflex femoral and lateral circumflex femoral arteries, both usually branches of the deep artery of the profunda femoris.

The blood supply to the hip has numerous variations and one or both of these arteries may arise directly from the femoral artery.

The trochanteric anastomosis, between the femoral artery or profunda femoris and the gluteal vessels provides most of the blood to the head of the femur.

The hip’s muscles act on three main axes, all of which pass through the center of the femoral head, and result in three degrees of freedom and three pair of principal directions:

Flexion and extension occur around a transverse axis.

Lateral rotation and medial rotation around a longitudinal axis.

Abduction and adduction around a sagittal axis.

A combination of these movements, circumduction, is a compound movement.

Most anatomists define 17 hip 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 gluteal muscles include the gluteus maximus, gluteus medius, gluteus minimus, and tensor fasciae latae.

The gluteal muscles 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 muscles of the hip include: The adductor brevis, adductor longus, adductor magnus, pectineus, and gracilis.

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.

The iliacus and psoas major comprise the iliopsoas group.

The psoas major 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.

These muscles are commonly referred to as the iliopsoas.

The Lateral rotator group consists of the externus and internus obturators, the piriformis, the superior and inferior gemelli, and the quadratus femoris.

These six muscles originate at or below the acetabulum of the ilium and insert on or near the greater trochanter of the femur.

The rectus femoris and the sartorius, can cause some movement in the hip joint, but primarily move the knee, and not generally classified as muscles of the hip.

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

Hip movement is a function of multiple muscles being activated at once, and these muscles are also responsible for more than one type of movement.

The movement that brings the thighs close to the abdomen is called flexion.

When the legs open, it is called lateral rotation.

When the legs close the movement is 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.

The psoas is the primary hip flexor, assisted by the iliacus, but the pectineus, the adductors longus, brevis, and magnus, as well as the tensor fasciae latae are also involved in flexion.

The main hip extensor is the gluteus maximus, 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.

The lateral rotator group causes lateral rotation of the thigh.

The lateral rotator muscle group are aided by the gluteus maximus and the inferior portion of the adductor magnus.

Hips muscles help maintain the standing posture, working 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.

Hips muscles that help maintain standing posture 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.

Some of the hip muscles also act on either the vertebral joints or the knee joint.

A hip fracture refers to a break that occurs in the upper part of the femur.

A hip fracture’s symptoms may include pain around the hip particularly with movement and shortening of the leg.

The hips of human females widen during puberty.

The femora are also more widely spaced in females, so as to widen the opening in the hip bone and thus facilitate childbirth.

In females, the ilium and its muscle attachment are shaped so as to situate the buttocks away from the birth canal, where contraction of the buttocks could otherwise damage the baby.

The female hips have long been associated with both fertility and general expression of sexuality.

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