Ball and socket joint Ball and socket joint The ball and socket joint (or spheroid joint) is a type of synovial joint in which the ball-shaped surface of one rounded bone fits into the cup-like depression of another bone. The distal bone is capable of motion around an indefinite number of axes, which have one common center. It enables the bone to move in many places (nearly all directions). An enarthrosis is a special kind of spheroidal joint in which the socket covers the sphere beyond its equator. Examples of this form of articulation are found in the hip, where the round head of
Capsule of hip joint Capsule of hip joint The articular capsule (capsular ligament) is strong and dense. Above, it is attached to the margin of the acetabulum 5 to 6 mm. beyond the labrum behind; but in front, it is attached to the outer margin of the labrum, and, opposite to the notch where the margin of the cavity is deficient, it is connected to the transverse ligament, and by a few fibers to the edge of the obturator foramen. It surrounds the neck of the femur, and is attached, in front, to the intertrochanteric line; above, to the base of the neck; behind,