|Henry Gray (18251861). Anatomy of the Human Body. 1918.|
Amphiarthroses (slightly movable articulations).In these articulations the contiguous bony surfaces are either connected by broad flattened disks of fibrocartilage, of a more or less complex structure, as in the articulations between the bodies of the vertebræ; or are united by an interosseous ligament, as in the inferior tibiofibular articulation. The first form is termed a symphysis (Fig. 298), the second a syndesmosis.
FIG. 298 Diagrammatic section of a symphysis. (See enlarged image)
Diarthroses (freely movable articulations).This class includes the greater number of the joints in the body. In a diarthrodial joint the contiguous bony surfaces are covered with articular cartilage, and connected by ligaments lined by synovial membrane (Fig. 299). The joint may be divided, completely or incompletely, by an articular disk or meniscus, the periphery of which is continuous with the fibrous capsule while its free surfaces are covered by synovial membrane (Fig. 300).
FIG. 299 Diagrammatic section of a diarthrodial joint. (See enlarged image)
FIG. 300 Diagrammatic section of a diarthrodial joint, with an articular disk. (See enlarged image)
| The varieties of joints in this class have been determined by the kind of motion permitted in each. There are two varieties in which the movement is uniaxial, that is to say, all movements take place around one axis. In one form, the ginglymus, this axis is, practically speaking, transverse; in the other, the trochoid or pivot-joint, it is longitudinal. There are two varieties where the movement is biaxial, or around two horizontal axes at right angles to each other, or at any intervening axis between the two. These are the condyloid and the saddle-joint. There is one form where the movement is polyaxial, the enarthrosis or ball-and-socket joint; and finally there are the arthrodia or gliding joints.|
Ginglymus or Hinge-joint.In this form the articular surfaces are moulded to each other in such a manner as to permit motion only in one plane, forward and backward, the extent of motion at the same time being considerable. The direction which the distal bone takes in this motion is seldom in the same plane as that of the axis of the proximal bone; there is usually a certain amount of deviation from the straight line during flexion. The articular surfaces are connected together by strong collateral ligaments, which form their chief bond of union. The best examples of ginglymus are the interphalangeal joints and the joint between the humerus and ulna; the knee- and ankle-joints are less typical, as they allow a slight degree of rotation or of side-to-side movement in certain positions of the limb.
Trochoid or Pivot-joint (articulatio trochoidea; rotary joint).Where the movement is limited to rotation, the joint is formed by a pivot-like process turning within