Bacteria inside the flexor tendon sheath is one of the few true emergencies in the hand. Kanavel’s four signs identify it in under a minute, and the wound that let it in is often too small to remember.
Two common finger infections that get confused. Paronychia sits at the nail fold and often settles early. A felon sits in the fingertip pad, builds pressure in a closed compartment, and needs draining before it reaches bone.
The dog bite that looks terrible is usually the least dangerous. A cat’s puncture and a small split over a knuckle from someone’s tooth are the two that reach joints and tendons, seal bacteria in, and cost people fingers.