What are the major joint types?
Fixed joints are where 2 or more bones meet, but don't move. A good example would be the skull plates after the first year of life. They are stuck together and don't move.
Slightly movable joints have cartilage between them. They move a little, but ligaments keep them from moving too far. An example of a slightly movable joint is the connections between 2 vertebrae in the spine.
Freely movable joints are joints like elbows and knees. There are multiple types of movable joints depending on which direction they allow movement.
What are the types of freely movable joints?
Ball-and-socket joints allow movement in all directions, including rotation. One bone has a ball-shaped end that sits in a round "socket." The shoulders and hips are this type of joint.
Condyloid joints are similar to ball-and-socket joints, but they don't allow rotation. An example would be the joints of your knuckles. You can move your fingers up, down, right and left, but you can't rotate them.
Gliding joints allow sliding of the bone surfaces. The group of bones in the wrist (carpals) and in the ankle (tarsals) are an example.
Hinge joints allow movement back an forth like a door. Your knees and elbows are an example.
Pivot joints allow only rotation. The radial head in the elbow is an example.
Saddle joints allow movements in many directions... imagine sitting on a horse saddle... you can lean and fall of in different directions. The joint at the base of the thumb is an example.
What holds joints together?
Joints are held together by ligaments and by forces created by muscles. Many joints have a capsule of ligaments that holds the end of the bone in place.
What are bursa?
Bursa are sacks of clear fluid that help cushion joints and ligaments. Inflammation of the bursa is called "bursititis."
Last Updated (Friday, 10 July 2009 08:43)