Hip Joints

Hip Joints

The hip joints are also known as the coxal joints. They are ball-and-socket joints with less range than those of the shoulder. Although widely ranging movements are possible, they are limited by the deep hip sockets and strong ligaments. Each hip joint is formed by the artic-ulation of the femur’s spherical head with the hip bone’s acetabulum and its deeply cupped position (­FIGURE 8-5). A circular rim of fibrocartilage called the acetabular labrum increases the depth of the acetabulum. Hip joint dislocations are rare because the ­articular surfaces fit tightly together. The labrum’s diameter is less than that of the head of the femur, however.

Each hip joint is completely enclosed by its thick articular capsule, which extends from the rim of the ace-tabulum to the femur neck. The capsule is reinforced by the iliofemoral ligament, pubofemoral ligament, and ischiofemoral ligament. The iliofemoral ligament lies anteriorly and is very strong, with a V-shape. The pubofemoral ligament is a triangular thickening of the inferior area of the capsule. The ischiofemoral ligament spirals posteriorly. All three ligaments have an arrange-ment that causes a screw-like turning motion of the femur head into the acetabulum when a person stands up straight. They provide increased joint stability.

The ligamentum teres, which is the ligament of the femur head, is the flattened intracapsular band connecting the femur head to the acetabulum’s lower edge. During most movements of the hip, it is slack. It is not important in joint stabilization, but contains an artery supplying the head of the femur. When the artery is damaged, severe hip joint arthritis may develop. Stability of the hip joint comes from the deep socket that strongly encloses the femur head, strong capsular ligaments, thick hip and thigh muscles sur-rounding it, and muscle tendons crossing it.