A tricky trigger finger: a patient with intermittent intrinsic locking of a metacarpophalangeal joint.

A trigger finger is not always caused by a stenosing tenosynovitis, but may rarely be due to an internal derangement of the metacarpophalangeal (MCP) joint. Several different mechanisms may be responsible for this intrinsic joint locking. A patient is described with intermittent locking of an index MCP joint due to an osteophyte tethering the radial accessory collateral ligament. Removal of the osteophyte solved the problem. Awareness of this condition may prevent unnecessary exploration of the proximal pulley and tendon sheath.