Which muscle is the prime mover for flexion at the distal interphalangeal joints (DIP) of the fingers?

Which muscle is the prime mover for flexion at the distal interphalangeal joints (DIP) of the fingers?

• A. Extensor Digitorum
• B. Abductor Pollicis Longus
• C. Flexor Digitorum Profundus
• D. Flexor Digitorum Superficialis

Answer: (C)

Distal interphalangeal joint flexion is produced mainly by the flexor digitorum profundus. This deep flexor sends tendons to the distal phalanges, so when it contracts it pulls on the fingertips to bend the DIP joints. The flexor digitorum superficialis, which inserts on the middle phalanx, mainly flexes the proximal interphalangeal joints and has only a limited, indirect role in DIP flexion. The extensor digitorum lies on the back of the hand and extends the fingers, not flexes them, while the abductor pollicis longus acts on the thumb, not the other fingers. So the profudus is the primary driver for bending the DIP joints.

Distal interphalangeal joint flexion is produced mainly by the flexor digitorum profundus. This deep flexor sends tendons to the distal phalanges, so when it contracts it pulls on the fingertips to bend the DIP joints. The flexor digitorum superficialis, which inserts on the middle phalanx, mainly flexes the proximal interphalangeal joints and has only a limited, indirect role in DIP flexion. The extensor digitorum lies on the back of the hand and extends the fingers, not flexes them, while the abductor pollicis longus acts on the thumb, not the other fingers. So the profudus is the primary driver for bending the DIP joints.