Inflammation is characterized by erythema, warmth, pain, and edema. Acute in-flammation generally occurs in response to an injury or introduction of foreign mate- rial at a specific site and is an important part of wound healing.  Chronic inflammation is usually associated with a systemic disease process, such as rheumatoid arthritis (RA), and itself can be a major source of disability. When inflammation affects the joints of the musculoskeletal system, it most often affects the synovial membrane, resulting in a condition called synovitis. Inflammation may also affect tendons or tendon sheaths (tendinitis); it also can occur extra-articularly in bursae (bursitis).

While acute inflammation is often a health- ful response and usually is self-limiting, chron- ic inflammation, as in arthritic disease, can be harmful. For example, inflammation can de- stroy the cartilage that cushions the bone. Pro- gressive cartilage destruction leads to joint in- stability and loss of function. Because of these harmful effects, inflammation should be in- hibited in certain circumstances. Knowing when and how to modulate inflammation de- mands an understanding of the cellular, bio- chemical, and molecular aspects of inflamma- tory processes and the regimens currently available to treat them.

This chapter describes the inflammatory process, how inflammation is triggered, how chronic inflammation affects the joints, and how it is ameliorated through endogenous and exogenous agents. In addition, the patho- physiology of several types of arthritis that are manifested through the inflammatory process are described, along with current trends in research aimed at targeting the mo- lecular and immunologic pathways of in- flammation.