Thumb metacarpophalangeal stress testing

Stress testing of the thumb MCP joint is performed to help identify injury to the collateral ligaments.

(A) A valgus stress that reveals laxity, especially when significantly greater than the uninjured contralateral thumb, suggests ulnar collateral ligament tear (skier's thumb).

(B) A varus stress that reveals laxity suggests radial collateral ligament tear, which is less common.

When performing the examination, the clinician should stabilize the thumb metacarpal with one hand and exert stress on the proximal phalanx with the other to ensure that motion stems from the MCP only.