The 46-year-old man showed up at hospital emergency room in Chicago, complaining that his left knee hurt. The X-rays above showed why.

Fourteen years earlier, he’d been shot in the knee. That’s the image on the left. The bullet was not removed, and over the years his knee had ground it into tiny pieces, as shown on the right.

The fragments got into the tissue that lines the knee, irritating the joint. The bullet also gave him a delayed form of lead poisoning.

Dr. Michael Schindlbeck, an emergency medicine specialist at the hospital, had never seen such an injury. The New England Journal of Medicine published the X-rays and a brief case description on Wednesday.