Hip

The hip is the part of the body located at the upper end of the leg, where the pelvis connects to the thighbone. It is the point from which walking, running, and sitting movements originate, and it is surrounded by large muscles that support the body's weight.

The term 'hip' in common usage has two meanings: the outer surface that is visible (on the side of the leg), and the bone joint inside (the hip joint). In medical and anatomical contexts, the hip joint is typically what is meant.

Structure of the joint

The hip joint is of the ball-and-socket type. The spherical head of the thighbone fits into a socket located in the pelvis. On both sides, a smooth layer of cartilage reduces friction, while fluid inside the joint facilitates movement.

Strong ligaments surround the joint and prevent the head of the thighbone from slipping out of the socket. For this reason, the hip is more stable than the shoulder, though its range of motion is somewhat more limited.

Function and movement

The hip allows the leg to move forward, swing side to side, rotate outward, rotate inward, and turn. The muscles of the leg and pelvis work together in these movements and also maintain balance when a person stands on one leg.

Health and injury

The hip joint can develop various conditions, including cartilage wear that increases with age, and fracture of the thighbone, which is common in elderly people with weak bones. When the joint is severely damaged, surgical hip replacement with an artificial joint is a standard treatment option.