Concept of the Week

The Structural and Functional Classification of Joints

Structurally, bones are classified according to the nature of the material that joins the bones together:

1. Fibrous Joints: The bone ends are united by collagenous fibers.

2. Cartilaginous Joints: The bone ends are united by cartilage (either fibrocartilage or hyaline cartilage).

3. Synovial Joints: The bone ends are covered with articular cartilage and enclosed within a joint capsule lined with synovial membrane.


Functionally, joints are classified according to the amount of movement permitted:

1. Synarthroses: Completely immovable joints (e.g. sutures)

2. Amphiarthroses: Slightly movable joints (e.g. interosseous membrane conncting radius to ulna)

2. Diarthroses: Joints that are freely movable in one or more planes of space (e.g. knee joint)

Term of the Day

Hilton's Law: Joints (articulations) have an extensive nerve supply. These articular nerves are actually branches of the nerves that supply the overlying skin and the muscles that move the joint. Hilton's Law essentially says that the nerves that supply a joint also supply the muscles that move the joint and the skin covering their attachments.