Dr. David J. Bozentka answers your questions about MP joint arthritis.
What is the MP joint?
The metacarpophalangeal (MP) joint is the large knuckle joint located where the fingers and thumb meet the hand (Figure 1). The metacarpal bones lie within the palm and the phalanges lie within the digits. The metacarpal head, or ball part of the MP joint, meets with the proximal phalanx which makes up the socket part of the joint. The bones on each side of the joint have a cartilage surface that allows smooth gliding. Multiple tendons cross this joint. Flexor tendons and small additional tendons in the hand promote flexion, or bending. The extensor tendons promote extension, or straightening, of the joint. A collateral ligament on each side of the joint provides stability for a pinching motion. The bones, ligaments, and tendons of the MP joint allow motion and stability for optimal hand function.