Partial flexion at the PIP joint with extension at the DIP joint is characteristic of which finger deformity?

Partial flexion at the PIP joint with extension at the DIP joint is characteristic of which finger deformity?

• A. Boutonniere Deformity
• B. Swan Neck Deformity
• C. Mallet Finger
• D. Jersey Finger

Answer: (A)

This pattern reflects an injury to the extensor mechanism at the middle joint (PIP). When the central slip of the extensor tendon over the PIP is damaged, the PIP can no longer stay straight and tends to bend (flex). The lateral bands then slide forward and pull on the distal joint (DIP), keeping it in extension. So you end up with the PIP in flexion while the DIP remains extended—classic boutonniere deformity. This presentation helps distinguish it from other finger deformities. Swan neck deformity shows the opposite pattern: the PIP is hyperextended while the DIP is flexed. Mallet finger involves an inability to extend the DIP, so the fingertip droops. Jersey finger is an injury where the flexor tendon to the fingertip is torn, causing loss of DIP flexion.

This pattern reflects an injury to the extensor mechanism at the middle joint (PIP). When the central slip of the extensor tendon over the PIP is damaged, the PIP can no longer stay straight and tends to bend (flex). The lateral bands then slide forward and pull on the distal joint (DIP), keeping it in extension. So you end up with the PIP in flexion while the DIP remains extended—classic boutonniere deformity.

This presentation helps distinguish it from other finger deformities. Swan neck deformity shows the opposite pattern: the PIP is hyperextended while the DIP is flexed. Mallet finger involves an inability to extend the DIP, so the fingertip droops. Jersey finger is an injury where the flexor tendon to the fingertip is torn, causing loss of DIP flexion.