When you think about your joints, you most likely think immediately of your knees, shoulders, hips, elbows, etc. Certainly these are large and important joints, but there are many other joints in the body that you may have never realized existed. For example, the union of the parallel borders of the radius and the ulna and the junction between a tooth and its socket are both types of joints.
A joint, or articulation, is defined as the junction between two or more bones of the skeleton. Joints can be classified in one of two ways: by the movement they permit or by the tissue joining the bones of the joint. Each of these systems of classification provides useful information about the joint, but the systems do not necessarily correspond.