Fig. 1

Legend, consequential pathology from long-term and/or repetitive TMC instability: The first site of pathology (1), the trapeziometacarpal (TMC) joint, will eventually sublux in the radial direction, causing chondral cartilage damage and creating a second site of pathology at the thumb metacarpophalangeal (MCP) joint. As the first phalanx is hyperextended in an attempt to compensate for the metacarpal subluxation relative to the carpal bone, the cartilage of the MCP joint becomes damaged (2). As a result, patients begin to notice marked weakness in the thumb, particularly with pinching and grasping tasks (3)