Joint is the location at which two or more bones make contact. Joints are classified into three groups as follows:
- Synarthrosis is the type of joint that is rigid and fixed. For example, the joints is skull.
- Symphysis (amphiarthrosis) is type of slightly movable joints. Foe Example, the joints composing spine.
- Diarthrosis is a type of joint which allows maximum movement. For Example, the joint between shoulder and upper arm bone. All the bones of diarthrosis joints are layered by smooth cartilage and lubricated by synovial fluid produced by bursa sack.
Diarthrosis joint is composed of several types of joint, which are as follows.
- Ball and socked joint, allowing widest range of motions, found is hips and shoulder.
- Hinge joint, allowing one direction movement, found in elbow, knee, and fingers.
- Pivot joint, allowing rotation around axis, found in the firs and second segment of spine, so that head can rotate.
- Gliding joint, allowing the surface of each bone slides in a short distance in its surface. This joint is found in the carpals of the wrist.
- Saddle joint, allowing two-direction movement just like a person sitting on the saddle. The joint is found in wrist bone and hand.