Which landmark in the palm is related to MCP joint flexion?

• A. Distal palmar crease
• B. Proximal palmar crease
• C. Thenar crease
• D. Lifeline crease

Answer: (A)

The key idea is that the creases on the palm reflect how the fingers move. The distal palmar crease sits across the palm at the level of the metacarpophalangeal joints, and it deepens when the fingers flex at those joints. That makes it the best marker for MCP joint flexion, since the crease forms with the bending of the fingers where the metacarpals meet the phalanges. The proximal palmar crease is higher toward the wrist and isn’t specifically tied to MCP flexion. The thenar crease is over the base of the thumb and relates more to thumb movement, not the MCPs of the fingers. The lifeline crease is a long palm crease that doesn’t indicate MCP joint motion.