In sports medicine, where injuries are typically torn muscles or tendons or narrow cracks in bones, specialists like Dr. Andrews and Dr. DiGiovanni say M.R.I.’s often are not needed — they usually can figure out what is wrong with just a careful medical history, a physical exam and, sometimes, a simple X-ray.

Image Dr. James Andrews found that M.R.I.'s can mislead. Credit... Karena Cawthon for The New York Times

M.R.I.’s are not the only scans that are overused in medicine but, in sports medicine, where many injuries involve soft tissues like muscles and tendons, they rise to the fore.

In fact, one prominent orthopedist, Dr. Sigvard T. Hansen, Jr., a professor of orthopedics and sports medicine at the University of Washington, says he pretty much spurns such scans altogether because they so rarely provide useful information about the patients he sees — those with injuries to the foot and ankle.

“I see 300 or 400 new patients a year,” Dr. Hansen says. “Out of them, there might be one that has something confusing and might need a scan.”

The price, which medical facilities are reluctant to reveal, depends on where the scan is done and what is being scanned. One academic medical center charges $1,721 for an M.R.I. of the knee to look for a torn ligament. The doctor who interprets the scan gets $244. Doctors who own their own M.R.I. machines — and many do — can pocket both fees. Insurers pay less than the charges — an average of $150 to the doctor and $960 to the facility.

Steve Ganobcik is something of a poster child for what can go wrong with the scans. A salesman who turns 44 on Saturday, Mr. Ganobcik twisted his knee skiing in Colorado in February. He continued skiing anyway and skied again the next two days as well, not wanting to cut his vacation short.

When he got home to Cleveland, his knee still bothered him, so he saw a sports medicine orthopedist. The doctor immediately ordered an M.R.I. and said it showed a torn anterior cruciate ligament, or A.C.L. It is one of the most common — and most devastating — sports injuries. The standard treatment is surgery, with a difficult recuperation lasting six months to a year.