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.

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The patient — a chronic alcoholic who performed poorly on a cognitive test — was given intravenous treatments to absorb the lead in his body. Doctors operated to remove the lining of his knee containing the bullet fragments.

But the man eventually disappeared. The last time the doctors saw him was in August.

Why was the bullet left in the first place? Leaving bullets in place “is actually more the norm than the exception” for trauma surgeons, Dr. Schindlbeck said.

The real problem with bullets is the holes they leave behind. Trying to remove a bullet can make the wound still worse.

“Aggressively seeking and removing bullets in the operating room is more appropriate for Hollywood drama than practical medicine,” Dr. Schindlbeck said.

One exception to that rule is a bullet lodged in a large joint like the knee. Then removal is mostly routine. Or ought to be.

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