A joint is the point where two or more bones meet i.e the bones of the body are attached together by joints. All joints are lubricated with an oily liquid (synovial fluid) around them to reduce friction and make it easy for one bone to move against another. Depending on the degree of movement, joints can be classified into movable and immovable joints.
Movable Joints:
In movable joints, movement of the body is possible to some extent. There are four types of movable joint:
Ball and socket Joint:
This is the kind of joint found in the shoulder and hips of human beings. Such a joint allows the bones to move and turn in all directions.
Hinge Joint:
Hinge joints are found at the knee and in the fingers and toes of animals. Such a joint allows movement in one direction. Hinge joints are also called synovial joints because they have a synovial cavity.
Pivot Joint:
Pivot joints are especially suited for rotating movements. The movement between the first two cervical vertebrae in the pivot joint enables the head to turn from side to side. The neck is a pivot joint that allows rotation.
Gliding Joint:
Gliding joints allow one set of bones to twist or slide on another set e.g wrist and ankle joints.
Immovable Joints:
The bones fit closely together and there is no movement e.g suture joint. The suture joint is a type of fibrous joint that unites most bones of the skull.
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