A joint is the point at which two bones are connected. Many joints
provide support and stability and allow movement, although some, such as those
of the pelvis, are not movable.
Joints contain bones, cartilage, and a lining called synovium,
which produces a lubricating fluid. Most joints are held together by muscles,
tendons, and ligaments and are often cushioned by fluid-filled sacs called
There are several types of joints, including:
Hinge joints, such as the elbows and
Ball-and-socket joints, such as the hips and
Pivot joints, which allow rotation. For example, the
joints in the neck allow the head to turn from side to
Condyloid joints, such as the wrist, which allow movement in
many different directions.
Anne C. Poinier, MD - Internal Medicine & Nancy Ann Shadick, MD, MPH - Internal Medicine, Rheumatology