Metakarpalknoglen

Metakarpalknoglen, known in English as the metacarpophalangeal joints (MCP joints), are the articulations between the heads of the metacarpal bones and the proximal phalanges of the fingers. There are five MCP joints in each hand, one for each finger, with the first (thumb) MCP joint having some functional differences but sharing the same general role in finger movement. These joints are synovial and typically described as ellipsoid (condyloid) joints, allowing a combination of movements that support a wide range of hand function.

The articular surfaces consist of convex heads of the metacarpals and concave bases of the proximal phalanges, enclosed by a fibrous joint capsule. The joint is strengthened by collateral ligaments on its sides—radial and ulnar collateral ligaments—that tighten in specific directions to stabilize the finger laterally. A thickened anterior (volar) plate or palmar plate reinforces the palmar aspect of the joint, helping to prevent hyperextension and to distribute load across the joint during grasping. The extensor mechanism crosses the MCP joints and coordinates finger extension, while flexors attach to the palmar side to produce flexion.

Movements at the MCP joints include flexion and extension (with the typical range allowing about 90 degrees of flexion and slight hyperextension at rest in many individuals), as well as some abduction and adduction, particularly in digits 2–5. Circumduction is possible to a limited extent due to the joint’s oblique axes and the supporting soft tissues.

Clinical relevance includes injuries from trauma such as jammed fingers or dislocations, and chronic conditions like rheumatoid arthritis or osteoarthritis, which can alter alignment, stability, and function of the MCP joints. Proper biomechanics of these joints are essential for grip, pinch, and fine motor tasks.