I.                  The Normal Hip Joint in Dogs

The hip is a ball-and-socket joint where the leg and the body meet.  The hip joint is called the coxofemoral joint.  At the top of the leg bone, or femur, is a ball called the femoral head.  The femoral head is attached to the rest of the femur by the femoral neck.  The femoral head sits in a socket, or cup, in the pelvis called the acetabulum.

Like all synovial joints, the hip joint has a joint capsule covered on the inside by the synovial membrane.  The synovial membrane makes synovial fluid, which helps to lubricate the joint.  The femoral head and the acetabulum are covered by cartilage which acts as a shock absorber in the joint.