Arthritis consists of more than 100 different condition which range from relatively mild forms of tendinitis and bursitis to crippling systemic forms, such as rheumatoid arthritis. It includes pain syndromes such as fibromyalgia and arthritis-related disorders, such as systemic lupus erythematosus, that involve every part of the body. Other forms of the disease, such as gout, are almost never thought of as arthritis, while osteoarthritis is often thought to be the only form of this disease.

The common denominator for all of these conditions is joint and musculoskeletal pain, which is why they are grouped together as 'arthritis.' Often this pain is a result of inflammation of the joint lining. Inflammation is involved in many forms of arthritis and is the body's natural response to injury. The warning signs presented by inflammation are redness, swelling, heat and pain. When a joint becomes inflamed, it may get any or all of these symptoms. This can prevent the normal use of the joint and therefore it can cause the loss of function of that joint.