enarthrosis

An enarthrosis is a special kind of spheroidal joint in which the socket covers the sphere beyond its equator.

A ball and socket joint (enarthrosis, spheroidal joint) is a joint in which the ball-shaped surface of a bone fits into the cup-like indentation of another bone.

Diarthroses can in turn be classified into six groups according to the type of movement they allow: arthrodia, enarthrosis, ginglymus, rotary diarthrosis, condyloid articulation and articulation by reciprocal reception.

The bony surfaces would of themselves constitute an enarthrosis and allow movement in all directions, were it not for the annular ligament, by which the head of the radius is bound to the radial notch of the ulna, and which prevents any separation of the two bones laterally.