Each year, more than 28 million MRIs are performed in the U.S. to detect everything from tumors to brain aneurysms. They're also widely used in sports medicine to diagnose torn or damaged tendons, ligaments, and muscles. And while the scans – which use powerful magnetic fields to produce detailed images of the body – are vital to identifying serious injuries, many orthopedists have come to believe that MRIs are overused and often detect issues that lead to unnecessary treatments and surgeries.

"Some [MRIs] are appropriate, but the vast majority are not," says Dr. Christopher DiGiovanni, a foot and ankle orthopedist at Brown University. Patients who see DiGiovanni either come with an MRI that another doctor ordered or ask that he prescribe one, he says. And when he does order a scan, "it's very rare for an MRI to come back with the words 'normal study.' I can't remember the last time I've seen it."

Because MRIs detect tiny changes in tissue, scans often find abnormalities that aren't problems or even the source of an injury. For example, half of all middle-aged people with no shoulder pain have partially torn rotator cuffs. If you have shoulder pain and an MRI reveals a torn cuff, there's no way to tell if the tear is causing the pain or is simply a normal part of aging. Either way, the treatment is to rest, avoid motions that hurt, and do strengthening exercises. "You don't need a scan for that," says Dr. Volker Musahl, an orthopedic surgeon at the University of Pittsburgh Medical Center.

Typically, patients consult orthopedic doctors when pain keeps them from exercising. If a runner's foot hurts, a swimmer's shoulder throbs, or a bicyclist's knee aches, for many doctors, the first step is to order an MRI to help identify the injury and the extent of the damage. Sometimes, these scans are useful: They can affirm a doctor's suspicion of a torn ACL or other traumatic injury, or provide a patient with a confirmed diagnosis and a sense of relief, even if the treatment remains the same.

Many times, though, the treatment doesn't remain the same. MRIs often expose abnormalities that require surgery or other aggressive procedures. Take the example of a patient who saw Dr. Jordan Metzl, an orthopedist at New York's Hospital for Special Surgery, for a second opinion. His first orthopedist ordered an MRI, which found ripped cartilage under his kneecap, and recommended major surgery. Upon examining him, Metzl realized that the man had a minor overuse injury and no operation was necessary. "Many things that show up on MRIs are of no clinical relevance," he says. "Surgery to fix the MRI finding and not the patient is becoming increasingly common."

Many orthopedists order MRIs because they feel compelled to offer something other than an old-fashioned physical exam. "Orthopedists like to intercede," says Dr. Joseph Bernstein, an orthopedist at the University of Pennsylvania. Patients also like it when doctors give them something actionable, like a test or a prescription, rather than ask them to wait to heal. Doctors will even offer scans against their best judgment because patients expect them. Refusing a patient's demand for a scan "is a complete nonstarter," Bernstein says. "If you don't get the scan, some other doc will, and the patient will think you're an idiot for having 'missed' what the other doc found." But, he adds, "I do tell patients, 'Don't get this MRI just so you won't worry. If anything, it will make you worry more.'"

Some doctors may be under financial pressure to order MRIs because they generate revenue. Most medical centers won't reveal prices for scans, but one clinic estimates that the basic charge to a patient for a knee MRI is more than $1,700, plus $240 for interpreting the results. Insurers typically reimburse half the costs. Many doctors own MRI machines, in which case they get both the scan and the interpretation fees. Small practices that pay for their own machines may have extra motivation: The cost of an MRI machine is $300,000 to $1 million, and a scanning suite can run up to $500,000. It takes a lot of MRIs to break even.

Scans can also lead to what might be called the "professional athlete effect" – when patients want the same cutting-edge treatments used on elite athletes, believing such treatments are more effective. Take the recent popularity of PRP (platelet-rich plasma) injections, a procedure in which your own blood is injected into an injured area to try to speed healing. Today more than 500 hospitals offer PRP, even though studies fail to show it helps. But because athletes like Tiger Woods have had the procedure, patients request it, and doctors offer it, at prices often exceeding $1,000. Insurers generally don't pay for PRP, citing lack of evidence of benefits.

Despite the cost, a treatment that works on a pro athlete may not even work on you, because they often recover more rapidly than amateur athletes. "Elite athletes can make you look good as a physician," says Dr. James Andrews, a sports medicine orthopedist in Gulf Breeze, Florida. "They have an ability to get better really fast. It has to do with genes, natural ability, and motivation."

Pros will also choose expedited treatments like cortisone injections to try to return to play as quickly as possible, overlooking long-term effects. Cortisone shots are able to mask pain so athletes can play, but they can also damage healthy tissue over time. Because coaches and doctors are under pressure to get athletes back on the field, they advocate risky or unproven treatments that may do more harm than good. "[Regular patients] think we can reconstruct just about any injury they have," Andrews says. "But we have to bring them back to Earth. Because a famous football player tore up his knee and went back to play, they think they can do the same."

Some of Andrews' patients see him about Tommy John surgery, which many pro baseball players undergo to repair damaged elbow ligaments. But most think better of it after Andrews tells them that 10 percent to 15 percent of patients don't fully recover from the procedure or return completely to playing, and those who get better usually take a year to do so. And if a patient just waits and rests, he often gets better on his own in four to six months, especially if the injury is minor. In short, Andrews says, an operation that sounds like a solution may not be necessary.

The best advice may be to consider your options and choose less medical care when reasonable, Musahl says. If you have an overuse injury – a sore shoulder from swimming, aching knees from running – cut back on exercise for a while and wait. Most overuse injuries heal on their own, and depending on the injury, doctors often don't have a reliable treatment. If a doctor offers you an MRI, be cautious. "Ask the doctor, 'What are you expecting to see on the MRI, and what would you do about it?'" Musahl says. "If you get an 'I don't know,' I would wait."

Bernstein advises asking your orthopedist if he or a colleague has had the suggested treatment. Not every sports injury gets better without treatment; this question can help sort things out. For instance, Bernstein has performed ACL surgery on a colleague. "There are proven effective operations," he says, "but there are other treatments in our bag of tricks that probably don't deserve that label."

Howard Wainer, an avid swimmer, saw Bernstein for a second opinion after an orthopedist recommended surgery for a partially torn rotator cuff, discovered by an MRI. Bernstein considered his case and recommended physical therapy for three months before thinking about surgery. "I went with little hope," Wainer says. But after three months of therapy and staying out of the water, Wainer was back to swimming, pain-free.