The hip bones are divided into 5 areas, which are:
A synovial joint that can produce movement around more than one axis is called a multiaxial joint.
The hip joint (latin articulatio coxae) is a synovial joint formed by the articulation of the rounded head of the femur and the cup-like acetabulum of the pelvis. It is classified as a ball and socket joint. It forms the primary connection between the bones of the lower limb and the axial skeleton of the trunk and pelvis. Both 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 and the joint may not be fully ossified (the process of forming bone) under the age of 25 years. The depth of the acetabulum is increased by a fibrocartilaginous rim called a labrum that grips the head of the femur and secures it in the joint. The acetabulum is oriented inferiorly, laterally and anteriorly. The magnitude of inferior orientation can be assessed using a line connecting the lateral rim of acetabulum and center of femoral head. This lines forms an angle with vertical known as center edge angle or angle of Wiberg. The magnitude of anterior orientation is referred as angle of acetabular anteversion.
The large head of the femur is completely covered in hyaline cartilage except for a small area called the fovea or pit. This is the site of attachment for an intracapsular ligament (called the ligamentum teres) that attaches directly from the head of the femur to the acetabulum. The head of the femur is attached to the shaft by a thin neck region that is often prone to fracture in the elderly, which is mainly due to the degenerative effects of osteoporosis.
The strong but loose fibrous capsule of the hip joint permits the hip joint to have the second largest range of movement (second only to the shoulder) and yet support the weight of the body, arms and head. The capsule is attached proximally to the entire periphery of the acetabulum beyond the acetabular labrum. The capsule covers the femoral head and neck like a sleeve and attaches to the base of neck. The 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. As the line of gravity falls posterior to the axis of the hip joint, the combined weight of the body seeks to extend the hip joint in normal standing and make the trunk fall backwards to the ground. To resist the stretching action on the anterior joint capsule in normal upright posture, the hip has two very strong anterior ligaments.
The hip joint is reinforced by three main ligaments.
There is also a small ligament called ligamentum teres or the ligament of the head of the femur. The ligament is a triangularly shaped band with its base on both sides of peripheral edge of acetabular notch. This structure is not that important as a ligament but can often be vitally important as a conduit of a small artery to the head of the femur. This arterial branch is not present in everyone but 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 hip joint is supplied with blood from the medial circumflex femoral and lateral circumflex femoral arteries, which are both usually branches of the deep artery of the thigh (profunda femoris), but may also arise directly from the femoral artery. There is also a small contribution from a small artery in the ligament of the head of the femur which 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 (e.g. through fracture of the neck of the femur along their course).
The hip has two anatomically important anastomoses, the cruciate and the trochanteric anastomoses. These exist between the femoral artery or profunda femoris and the gluteal vessels.
The muscles that cause movement in the hip can be divided into five groups according to their orientation around the hip joint:
Many of the hip muscles are responsible for more than one type of movement in the hip, as different areas of the muscle act on tendons in different ways.
The female hips have long been associated with both fertility and general expression of sexuality. Since broad hips facilitate child birth and also serve as an anatomical cue of sexual maturity, they have been seen as an attractive trait for women for thousands of years. Many of the classical poses women take when sculpted, painted or photographed, such as the Odalisque, serve to emphasize the prominence of their hips. Similarly, women's fashion through the ages has often drawn attention to the girth of the wearer's hips.