Joints, or articulations, are places where two or more bones attach.
There are three basic types of joints classified by the level of allowed movement:
Synarthrotic - are immovable articulations, such as the sutures in the skull, formed by the fusion of two bones
Amphiarthrotic - slightly movable articulations, joined with cartilage between them
ex: Symphysis Pubis between the two Pubis bones of the Pelvis
Diarthrotic - freely movable articulations, contain joint capsule and layers of cartilage over the ends of the two joining bones
ex: shoulder, elbow, wrists...
The basic structure of all diarthrotic joints are the same:
- cartilage lines the ends of the bones meeting at the joint to prevent friction
- synovial membranes line the joint and secretes synovial fluid for lubrication to aid in smooth movement
- the individual bones are connected together via ligaments, and attach to the muscles which move them via tendons