Joints - mobile bone joints. Structure, functions

Joints are part of the human musculoskeletal system, which also includes bones, interosseous joints, ligaments, muscles, fascia and tendons. The musculoskeletal system is responsible for maintaining posture and movement.

The articular surface, covered by articular cartilage with an average thickness of 0.5 to 2 millimetres, reduces friction during movement and is elastic, thereby reduces the risk of injury to the limb. Another element is the joint capsule that connects the joint surfaces and surrounds the joint. The capsule stabilizes the joint and protects it from excessive bone shifts. It consists of a fibrous and synovial membrane. The fibrous membrane determines the range of motion for the joint. The synovium is responsible for creating synovial fluid that fills the spaces between adjacent joint surfaces. The fluid minimizes friction of joint surfaces.

The articular cavities collect the joint fluid and are also responsible for maintaining proper intra-articular pressure. Inflammation causes the cavities to enlarge and accumulate more fluid, hence swelling in the joints during injuries.

Joint diseases are primarily:

- Sprain -( torsion/distortion) occurs when as a result of rapid movement the joint exceeds the range of motion that is safe. The effect of sprain can be damage to the joint capsule, cartilage, ligaments and tendon attachments. Sometimes bone fragments are also damaged

- Dislocation is a more serious sprain. When dislocated, the joint surfaces lose their connectivity, the ligaments, cartilage and menisci, as well as the joint capsule are damaged (strains or breaks)

- rheumatoid arthritis (chronic rheumatoid arthritis)

- psoriatic arthritis

Arthritis (gout)

- osteoarthritis