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A joint is the location at which two or more bones make contact. They are constructed to allow movement and provide mechanical support, and are classified structurally and functionally.

Classification

Terms ending in the suffix -sis are singular and refer to just one joint, while -ses is the suffix for pluralization.

Structural classification

Structural classification names and divides joints according to how the bones are connected to each other. There are three structural classifications of joints:

• fibrous joint - joined by fibrous connective tissue
• cartilaginous joint - joined by cartilage
• synovial joint - not directly joined

Functional classification

Joints can also be classified functionally, by the degree of mobility they allow:

• synarthrosis - permits little or no mobility. Most synarthrosis joints are fibrous joints (eg The Skull).
• amphiarthrosis - permits slight mobility. Most amphiarthrosis joints are cartilaginous joints (eg. Vertebrae).
• diarthrosis - permits a variety of movements. All diarthrosis joints are synovial joints (eg. Shoulder, Hip, Elbow, Knee etc), and the terms "diarthrosis" and "synovial joint" are considered equivalent by Terminologia Anatomica.

Biomechanical classification

Joints can also be classified based on their anatomy or on their biomechanical properties. According to the anatomic classification, joints are subdivided into simple and compound, depending on the number of bones involved, and into complex and combination joints:

1. Simple Joint: 2 articulation surfaces (eg. shoulder joint, hip joint)
2. Compound Joint: 3 or more articulation surfaces (eg. radiocarpal joint)
3. Complex Joint: 2 or more articulation surfaces and an articular disc or meniscus (eg. knee joint)

Anatomical

The joints may be classified anatomically into the following groups:

1. Articulations of hand
2. Elbow joints
3. Wrist joints
4. Axillary articulations
5. Sternoclavicular joints
6. Vertebral articulations
7. Temporomandibular joints
8. Sacroiliac joints
9. Hip joints
10. Knee joints
11. Articulations of foot

Arthritis

Main: Arthritis Arthritis and direct physical trauma to a joint are the causes of joint damage. Arthritis is a group of conditions where there is damage caused to the joints of the body. Arthritis is the leading cause of disability in people over the age of 55.