Hip Joint (Posterior View)

The hip joint helps retain balance and support the weight of the body in all of its movements. The upper end of the femur is rounded into a ball (or head of the femur) that fits into a socket in the pelvis to form the hip joint. The neck of the femur gives the hip joint a wide range of movement, but it is a point of weakness and a common site of fracture.

If a knee or hip joint breaks in an accident or wears out in old age,...

Anatomy Explorer

Full Hip Joint (Posterior View) Description

[Continued from above] . . . a surgeon can replace it with a ball-and-socket joint made from metal and  plastic and engineered in such a way that it will duplicate the motions of a human joint. Hip replacement was once impossible because, although joints could easily be produced in a laboratory, the human body rejected the materials that these joints were made of. Sometimes the pins that held the artificial joint to other bones worked loose and required more surgery. Some joints, especially the artificial knee, didn't work very well because they were designed like hinges that just opened one way. Later, when the designers realized the knee needed to rotate, they produced a joint that would fulfill these movements as well.

Medical pioneers finally overcame bodily rejection by making the joints out of nonirritating, man-made materials. They have now perfected hip and knee replacements so that recipients are relieved of pain and can walk at a smoother pace.