Hip joints. 1866 illustration showing the anatomy of the pelvis and ball-and-socket joints of the hip. Fig. 1: pelvis, including the acetabula (lower left and right), the 'sockets' of the hip joints. Fig. 2: Rear view of the hip joint, showing the tendons. Fig. 3: femur (thigh bone) and femoral head (round, upper right), the 'ball' of the hip joint.