The human skeleton contains three types of joints, the areas where two or more bones come together: immovable, partly movable and synovial. The ends of the bones that make up synovial joints are covered in cartilage, which is connective tissue that provides cushioning between the ends of the bones. The human body has several different types of synovial joints.
One type of synovial joint is the hinge joint. It is formed by a rounded bone that articulates with the surface of another bone that is curved inward. The hinge joint has strong ligaments on either side that function to prevent side-to-side motion. The knees and elbows are examples of hinge joints.
Ball and Socket
The ball and socket is a type of synovial joint made up of the rounded end of one bone that fits into the hollowed-out area of another bone. The hip and shoulder joints are examples of ball and socket joints. They allow movement in all directions; forward and back, side to side, and rotation in both clockwise and counterclockwise directions.
The saddle joint is a synovial joint that is named because its shape resembles a horse saddle. The saddle joint allows rocking movement to occur over the axis in the middle of the joint. A saddle joint is at the base of each thumb.
Gliding joints are synovial joints formed by the flat surfaces of two bones. These surfaces glide on each other and their movement is limited by ligaments that attach bone to bone. Gliding joints are present between the small bones in the wrist (carpals), feet (tarsals) and spine (vertebrae).
Pivot joints are synovial joints that only allow rotation to occur. The two bones in the forearm, the ulna and radius, form a pivot joint at the top of the forearm. Ligaments hold these bones in place while the radius rotates on the ulna as the arm moves from a palm up to palm down position.
Joints that consist of multiple bones are called compound joints. These synovial joints include multiple joint surfaces of different shapes that allow more than one motion to occur at a time. Compound joints exist at the top of the spinal column where it meets the skull.
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