Joint

Joint

A joint or articulation (or articular surface) is the connection made between bones in the body which link the skeletal system into a functional whole. They are constructed to allow for different degrees and types of movement. Some joints, such as the knee, elbow, and shoulder, are self-lubricating, almost frictionless, and are able to withstand compression and maintain heavy loads while still executing smooth and precise movements. Other joints such as sutures between the bones of the skull permit very little movement (only during birth) in order to protect the brain and the sense organs.

Structure

Joints are mainly classified structurally and functionally. Structural classification is determined by how the bones connect to each other, while functional classification is determined by the degree of movement between the articulating bones. In practice, there is significant overlap between the two types of classifications.

Structural classification

Structural classification names and divides joints according to the type of binding tissue that connects the bones to each other. There are three structural classifications of joints:

• Fibrous joint - joined by dense irregular connective tissue that is rich in collagen fibers.
• Cartilaginous joint - joined by cartilage.
• Synovial joint - not directly joined, the bones have a synovial cavity and are united by the dense irregular connective tissue that forms the articular capsule that is normally associated with accessory ligaments.

Functional classification

Functional classification names and divides joints according to the type of movement they allow. There are three functional classifications of joints:

• Synarthrosis - permits little or no mobility. Most synarthrosis joints are fibrous joints.
• Amphiarthrosis - permits slight mobility. Most amphiarthrosis joints are cartilaginous joints.
• Diarthrosis - permits a variety of movements. All diarthrosis joints are synovial joints.

Clinical significance

Damage to joints can be extremely painful and can lead to loss of function and deformity. Joint injuries and diseases usually produce a stiff, aching, "arthritic" joint. Arthritis is a common joint disorder featuring inflammation. A joint is an area of the body where two bones meet. A joint functions to allow movement of the body parts it connects. Arthritis literally means inflammation of one or more joints.

See also

• Arthritis
• Synovial joint
• Cartilaginous joint
• Fibrous joint

External links

• Britannica article on Joints

Joint Resources
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