Which Beighton score criterion specifically assesses the thumb's ability to touch the forearm?

• A. Dorsiflexion of the fifth finger to 90 degrees
• B. Opposition of the thumb to the volar aspect of the forearm
• C. Hyperextension of the knees
• D. Palms placed flat on the floor

Answer: (B)

This item tests screening for generalized joint hypermobility using simple, reproducible moves. The specific check for how far the thumb can move is opposition of the thumb to the volar (palm-side) aspect of the forearm. During this test the patient tries to bring the thumb across the palm so that the thumb tip or pad touches the forearm itself; successful touching indicates greater thumb mobility and contributes to the Beighton score. This is distinct from the other maneuvers, which assess other joints: bending the little finger beyond 90 degrees tests finger mobility, hyperextending the knees or elbows checks those joints, and placing the palms flat on the floor with straight knees evaluates overall forward flexibility and spinal/limb hypermobility patterns.