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introductionstatpearls· Introduction· item NBK538343

The metacarpophalangeal (MCP) joint, also known as “the knuckle,” is formed by the metacarpal head and proximal phalanx articulation (see Image. Metacarpophalangeal Articulation). This multiaxial joint allows flexion, extension, abduction and adduction. The MCP joint also dynamically coordinates with the interphalangeal (IP) joint to perform thumb opposition and composite finger flexion. Various congenital or acquired deformities, sports-related injuries, and degenerative conditions can affect the MCP joint.