The largest number of movable joints in the body having a joint or synovial capsule filled with synovial membrane that secretes a viscous fluid called synovia containing glycoprotein, which serves to lubricate the smooth cartilage (articular) surfaces making contact with the two bones. Hence, it is sometimes referred to as a synovial joint. The classification of various diarthordial joints are given in the figure below
Diathrodial joints can be classified as simple (only two articulating surfaces; e.g., hip), compound (more articulating surfaces; e.g., wrist) and complex (two or more articulating surfaces, together with a fibrocaartilage; e.g., knee). Three diathrodial joints are illustrated: A. ball-and-socket (permits movement in three planes: abduction/adduction, flexion/extension, rotation; e.g., hip and shoulder joints), B. hinge (permits movement in flexion/extension plane; e.g., interphalangeal joints of feet and hand), C. condyloid (permits movement in flexion/extension plane and small rotations; e.g., knee). Other diathrodial joints are: ellipsoid joint (abduction/adduction, flexion/extension; e.g., radiocarpal articulation of wrist), plane (or gliding) joint (termed non-axial as it does not occur about an axis and consists of two flat surfaces that slide over each other to permit movement; e.g. carpal bones in hand), pivot joint (pronation, supination, rotation; e.g., superior and inferior radioulnar joints), and saddle joint (abduction/adduction, flexion/extension, small amount of rotation; only found in the carpometacarpal articulation of the thumb). Finally, the contact areas between the articulating surfaces vary so that movement occurs through a range of motion (D). Other types of joints are: synarthrodial (or fibrous) joints (held together by fibrous articulations; e.g., sutures of the skull) and ampiarthrodial (or cartilaginous) joints (held together by epiphyseal plates or fibrocartilage; e.g., pubic symphysis). As with the synarthroidal joints, they have very limited movement (except, for example, when the synarthrodial joints move in the passage of the fetal head during delivery).
See Biomechanical degrees of freedom, Delivery position (presentation), Glycoproteins, Joint capsule, Pelvis/pelvic girdle