Mallet finger involves extensor mechanism at which joint?

• A. Distal interphalangeal joint
• B. Proximal interphalangeal joint
• C. Metacarpophalangeal joint
• D. Carpometacarpal joint

Answer: (A)

Mallet finger is a disruption of the extensor mechanism at the fingertip, specifically at the distal interphalangeal joint. When the extensor tendon (or its attachment on the distal phalanx) is injured, the tip cannot actively straighten and rests in a flexed position after an impact to the fingertip. The distal interphalangeal joint is the joint at the end of the finger just before the nail, whereas the other joints listed are more proximal (the proximal interphalangeal between the middle and proximal phalanges, the metacarpophalangeal at the hand, and the carpometacarpal at the base of the thumb).