Valgus stress testing of the thumb

The carpometacarpal (CMC) joint and the metacarpal bone of the thumb are securely grasped by one hand while the distal thumb is firmly grasped by the other. Using the thumbs for leverage, stress is applied across the metacarpophalangeal (MP) joint to the collateral ligament located on the ulnar side of the thumb (ie, the thumb is pulled away from the palm while the MP joint is braced).