In the human body, joints are commonly classified by the degree or range of mobility. The categories, and subcategories are as follows:
- SYNARTHROSIS (Immovable Joint)
This is a joint which is not designed for mobility, or designed to move only very slightly. Tough, fibrous connective tissue holds the bones of the joint together. An example is the sutures in the skull.
- Syndesmosis–a type of partially movable fibrous joint where two adjacent bones are connected by ligaments. An example would be the forearm, where the radius and ulna are tightly bound by the interossious ligament.
- AMPHIARTHROSIS (Semimovable joint)
This is a type of cartilaginous joint which is not typically designed to move very much. It is where bones are connected by cartilage or fibrocartilage. An example would be the intervetebral disks in the spine.
- DIARTHROSIS (Synovial / movable joint)
There are several categories of synovial joints:
These joints feature a synovial capsule which surrounds and lubricates the joint. Most of the joints in the human body are diartroses. Ligaments hold the bones in place and the surfaces of the bones which move against one another are capped with cartilage to prevent wear.
- Ball and socket – this sort of joint allows a free range of movement in many directions. Examples include the hip and shoulder.
- Hinge–Allows movement along a single axis only. Elbow and knee are examples.
- Saddle (Sellar)–the articulation of two concave bone surfaces, allows two axes of movement. The carpometacarpal joint of the thumb is an example of this sort of joint.
- Ellipsoid (Condyloid or Condylar)– this is similar to a ball and socket joint, but without significant rotation. Examples include the temporomandibular (jaw or TMJ) and radiocarpal (wrists) joints.
- Pivot–a ring and axis affair such as the atlas and axis at the base of the skull. Allows for rotation only.
- Gliding–flat surfaces which move across one another in one or two axes. The facet joints of the vertebrae or the joints between the small wrist (carpal) bones.
Kapit and Elson, “The Anatomy Coloring Book” (Addison-Wesley, New York, 1993).
Thibodeau and Patton, “Structure and Function of the Body,” eleventh edition, (Mosby, St. Louis, 1997).
Vannini and Pogliani (eds.), “the Color Atlas of Human Anatomy” (Beekman House, New York, 1980.
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