MP Joint Arthritis
The large joints in the hand at the base of each finger are known as the metacarpophalangeal (MP, or MCP) joints (see Figure 1). They act as complex hinge joints and are important for both power grip and pinch activities.
The MP joints are less often affected by arthritic conditions than the smaller joints in the hand or the joint where the thumb joins the wrist (CMC). The most common arthritic condition affecting the MP joints is rheumatoid arthritis. In this situation, the joint lining (synovium) produces chemical factors that inflame and destroy the cartilage and soft tissue, such as ligaments and tendons. The end result is that the joint surfaces are destroyed and the fingers drift into a characteristic ulnar-deviated position, in which they point towards the little finger.