- The metacarpophalangeal (MCP) joints of the hand are located between the metacarpals and the proximal phalanges of the fingers (including the thumb).
- There are five metacarpophalangeal joints named #1-5, from the lateral thumb side to the medial little-finger side.
- The metacarpophalangeal joints are synovial, diarthrotic, biaxial, condyloid joints.
- They allow:
- flexion/extension of the fingers in the sagittal plane.
- abduction/adduction of the fingers in the frontal plane.
- Abduction/Adduction of the fingers at the MCP joints are movement relative to an imaginary line through the middle of the middle finger when the middle finger is in anatomic position.
- The middle finger abducts in the frontal plane in both directions that it moves: radial abduction and ulnar abduction. The middle finger cannot adduct.
- Rheumatoid arthritis often manifests at the MCP joints with a characteristic ulnar deviation deformity.