An inflammation of a joint. The term covers more than 100 types of joint diseases. The most common and chronic types are osteoarthritis and rheumatoid arthritis. Arthritis may be a result of various causes, i.e., bacteria or infection.

Osteoarthritis is a degenerative disease associated with the aging process as a result of "wear and tear" on joint surfaces. Osteoarthritis commonly involves the joints subjected to the most stress, such as hips, knees, shoulders and spinal column (large and weight bearing joints).
Rheumatoid arthritis is a crippling, inflammatory disease of the joints. Onset of the disease is most common in people 20 to 40, and more than two-thirds are women. This progressive disease destroys the structure of joints and surrounding tissue. The entire joint becomes red, warm, painful, swollen, and eventually deformed.
Septic arthritis is caused by the invasion of a joint space by an infectious agent. The onset is usually sudden; the joint becomes acutely painful, hot, and swollen. Chills and fever are often present.