Four cardinal signs of slight finger flexion, fusiform swelling of the finger, pain on passive or active extension of the finger, and tenderness along the tendon sheath into the palm indicate:

• A. Paronychia
• B. Felon
• C. Purulent tenosynovitis
• D. Ganglion cyst

Answer: (C)

These signs point to infection inside the flexor tendon sheath of the finger, classic for purulent tenosynovitis. The finger held in slight flexion, the fusiform swelling along the entire finger, tenderness along the tendon sheath into the palm, and pain with passive extension all reflect inflammation directly around the flexor tendon as it travels within its sheath. When the sheath is infected, extending the finger stretches the irritated tendon, causing pain, and the sheath distends, producing the characteristic swelling.

This pattern helps distinguish it from other finger infections. Paronychia is an infection at the nail fold, presenting near the fingertip at the nail margin rather than along the tendon sheath. Felon is an infection of the fingertip pad with focal swelling and tenderness focused at the pulp, not along the tendon sheath. A ganglion cyst is a benign collection near a joint or tendon sheath that forms a lump, usually without the acute, sheath-centered tenderness and pain on extension seen here.

Because purulent tenosynovitis can progress rapidly and threaten tendon viability, it requires urgent evaluation and management, including antibiotics and usually surgical drainage.