The volar plate of the finger MCP joint is a fibrocartilaginous structure on the palmar surface of each metacarpophalangeal joint, connecting the distal metacarpal neck to the base of the proximal phalanx. It is thinner and less robust than the PIP volar plate and has a more flexible proximal attachment (the checkrein ligaments) that allows MCP hyperextension. The intrinsic muscles attach to its lateral borders.
Prevents MCP joint hyperextension, provides a smooth articular surface for the flexor tendons as they enter the fibro-osseous sheath, and anchors the proximal pulleys and collateral ligaments.
MCP volar plate injury produces hyperextension MCP dislocation, most commonly at the index MCP. Complex MCP dislocations (irreducible) occur when the volar plate becomes interposed between the metacarpal head and the proximal phalanx, often associated with the lumbrical muscle shifting dorsally. Simple MCP dislocations reduce with longitudinal traction; complex ones require open reduction to extract the interposed volar plate. In rheumatoid arthritis, MCP volar plate attenuation combined with collateral ligament weakness causes the characteristic ulnar drift and subluxation.
Dorsal MCP dislocation where the volar plate folds into the joint becomes irreducible by closed manipulation because traction widens the joint space allowing further volar plate interposition; open reduction through a volar incision extracts the plate from the joint and is followed by splinting in slight flexion.
