A joint is a juncture between two bones. There are different types:
- Immovable: An example would be the bones of the skull which are separated by tough fibers of cartilage
- Movable: Generally found in the limbs
- Hinge Joints: Provide forward and backward movement, such as the elbow or the knee
- Pivot Joints: Allow rotary movement such as the turning of the head from side to side
- Ball-and-socket Joints: Allow the greatest range of movement due to the round end of one bone fitting into the socket of the other separated only be elastic cartilage. Examples would be the hip or the shoulder.
- Fibrous: Connected by collagen fibers
- Synovial: Ease motion through the use of a lubricating liquid known as synovial fluid
Artificial joints has become increasingly common, particularly in hip and knee replacement as performed by orthopedic surgeons. Metal or plastic is used to relieve pain or correct joint deformity.