Finger Extension


Extension of the digits is a combination of extrinsic and intrinsic muscle action. The extrinsic extensors are primarily responsible for MCPJ extension, and the intrinsic extensors are primarily responsible for IPJ extension.

The long (extrinsic) extensors of the fingers are the extensor digitorum communis (EDC), reinforced by the extensor indicis and the extensor digiti minimi, joining the appropriate tendons of EDC on the ulnar side.

As the tendons pass over the MCP joints they are stabilised by tough transverse fibres called sagittal bands.

The tendons of the EDC terminate in each finger as an aponeurotic extensor expansion, covering the dorsum of the proximal phalanx and the side of its base. It attaches by a central slip into the base of each middle phalanx, and by two lateral slips to the base of each distal phalanx.