Joints & Movement
Discover the types of joints in the body and how their structure determines their range of motion.
Where bones meet
A joint, or articulation, is any point where two or more bones meet. Joints are classified by how much movement they allow and by the type of tissue that connects the bones.
Anatomy of a synovial joint
Synovial joints, like the knee and shoulder, contain a fluid-filled capsule that allows smooth, wide-ranging movement between bones.
Little to no movement
Bones are joined directly by fibrous connective tissue, as in the sutures of the skull.
Slight movement
Bones are joined by cartilage, allowing limited flexibility, as between vertebral discs.
Free movement
A fluid-filled joint capsule allows the greatest range of motion, as in the knee, hip, and shoulder.
Structure shapes function
A joint's shape, from hinge to ball-and-socket, determines the directions in which it can move.
Types of synovial joints
Synovial joints come in several shapes, each suited to a different kind of movement.
Joints under stress
Because synovial joints allow the most movement, they also bear significant mechanical stress, which is why cartilage, ligaments, and synovial fluid all work together to reduce friction and absorb shock.
More mobility often means less inherent stability.
Highly mobile joints like the shoulder rely more heavily on surrounding muscles and ligaments for stability than more restricted joints do.