The Pain in Her Hip Was Spreading Down Her Leg. What Could It Be?

“My hip hurts most of the time now,” the 20-year-old woman explained to Dr. Samantha Smith, a sports-medicine doctor at Yale New Haven Hospital and the second specialist she had seen since the pain in her left hip started two years earlier. She ran her hand down the side of her hip and over the thigh to her knee. It used to just happen at night, she continued. And only every now and then. But these past few months, the pain was present just about every day and absolutely every night.

It started sometime in the first flush of the pandemic in 2020. She was 18 and stuck at home. Her social life was limited, and she and her high school pals would work out together over FaceTime, moving to the beat of one of the exercise videos that went viral that summer. Her favorite was a brutal 20-minute drill of lunges and squats designed to build a better butt. At first, she wondered if she just pulled a muscle. The pain was dull and came on slowly as she lay in bed. She couldn’t pinpoint the exact location — it seemed as if her whole hip ached — but when she woke the next day, the pain was gone. She changed videos, and the pain went away, but not for long.

After weeks of this on-and-off ache, she mentioned it to her parents. They were doctors, and they peppered her with questions. It probably was some muscle injury, they agreed. She should take a few days off. And she did. But the pain kept its irregular nocturnal schedule. When rest didn’t work, she tried physical therapy. But the pain kept coming. Not every night, but often. And strangely, never in the daytime.

That fall she started college at Vassar. The excitement made her forget all about the pain — until just after Halloween, when her nights were interrupted once more. She signed up for more P.T. It didn’t help. The only thing that did help, she discovered, was ibuprofen. Indeed, a dose of that drug right before bed practically guaranteed a good night’s sleep.

Just before the Thanksgiving break, she had a video visit with her pediatrician. She moved her leg as her doctor instructed, rotating, lifting, kicking this way and that. All looked fine. She pressed and squeezed the various muscles. Again, fine. Her doctor sent her for an X-ray: normal. The doctor encouraged her to continue with P.T.

With the help of the prophylactic doses of ibuprofen, she made it through her first semester. But just as spring greened the branches of the Poughkeepsie campus, her nighttime pain drifted into her days. It wasn’t every day. It wasn’t all day. But it was now an intense pain. She carried her ibuprofen with her all the time. As the hours of her pain expanded, so too did its location. It crept from her hip down her thigh to her knee. And on really bad days, it strayed almost to her foot. Walking somehow made it better. If this was an injury, she thought, that didn’t make any sense. But really nothing about this pain made sense.

The girl’s mother was worried. During school breaks, she took her daughter to her pediatrician and to lots of physical-therapy appointments. It had to be a muscle problem. But why was she getting worse? One of the girl’s legs was slightly longer than the other. Was that the problem? Probably not, doctors and therapists assured her. Her daughter described an occasional clicking sensation in that hip when she stretched. Was it snapping-hip syndrome? If so, why hadn’t the therapy helped? Finally one friend had a recommendation: “You should take her to see Sam Smith.”

Smith trained in both adult and pediatric medicine at Yale New Haven Hospital and had followed that up with a year focused on sports medicine at the Hospital for Special Surgery in Manhattan before coming back to New Haven. “She is really the best doctor I know,” the friend said.

An Overlooked Abnormality

And so now, just a few weeks later, mother and daughter were in with Smith. Smith noticed that the patient had some tenderness at the top of the thigh bone, over the part of the bone that stuck out farthest, a prominence known as the greater trochanter. She was also tender down the side of her thigh, over what is known as the IT band, a thick strip of tissue that extends from the top of the hip bone — known as the iliac crest — down to the upper tip of the tibia. The IT band provides stability to the leg during strenuous activities like running and can be irritated by rubbing against the bony hip prominence.

Smith tested each of the muscles of the young woman’s hips and legs. The right leg was completely normal. But there was subtle weakness on the left. When asked to do a squat using only the right leg, the patient could do it easily, but she wobbled noticeably on the left. Smith gave the young woman a series of exercises designed to strengthen the specific muscles that were weak and scheduled her to come back in a month, just before she left for a semester abroad in England.

At the end of August, when mother and daughter returned, Smith was surprised to see that although the girl’s muscles were stronger, the pain hadn’t changed. So it wasn’t greater trochanteric pain syndrome; what else could it be?

The mother mentioned that there was an abnormality in one of the blood tests done when the pain first started. It was a marker of inflammation known as a C-reactive protein, or more familiarly, CRP. There are many reasons this protein can spike — physical trauma can do it; so can a minor infection. But a persistently elevated CRP would suggest something more than a muscle or ligament issue. That can be seen in autoimmune diseases or chronic infections, even cancer. No one knew what to make of it at the time, given that the X-ray was normal and the blood tests sent to look for infectious and rheumatologic causes of this kind of inflammation came back normal as well.

That could be an important clue, Smith said. She ordered a new X-ray and repeated the test. The results came back the following day: The X-ray again read as normal. But the CRP was now three times the level it had been. A whole new list of possibilities sprang to mind. Smith called the patient. She needed to get an M.R.I. of that hip.

The patient had her scan three days later. When she emerged, the technician told her that her doctor would be in touch.

There was something on the M.R.I., Smith told her. A tumor. She was pretty sure it was not malignant, but to be certain, the patient would need a CT scan. Smith explained that she thought the young woman had something known as an osteoid osteoma — an inflammatory tumor that can be seen in people her age. It hadn’t been what she was looking for, and an M.R.I. was not the best way to diagnose it. The young woman looked up the M.R.I. report on her electronic medical record. What she saw scared her. It was, as Smith said, a small tumor, but the report listed other, scarier possibilities as well. Most prominent on that list: cancer. An infection in the bone was also possible. The benign tumor that Smith suspected wasn’t even mentioned.

The CT scan was mercifully quick, and Smith called right away with the answer: It was an osteoid osteoma. Although these poorly understood tumors will resolve on their own after several years, most people who have them end up having them removed. The tumors are quite painful, and the treatment is simple and safe. Under CT guidance, a tiny catheter is introduced through the skin to the tumor, and a probe blasts the tumor with heat. Because the procedure is painful, it is usually done under general anesthesia.

Smith told me that she had seen three patients who had osteoid osteomas. Each time, she discovered it while looking for something else. The tumor is called the great mimicker because it looks like so many other possibilities that are more common or more dangerous.

The patient chose to defer the procedure until after her semester abroad. Then, just at the start of Hanukkah, she went to the operating room. Once the pain medicine she received at the hospital wore off, her hip hurt as it had never hurt before. Her parents discouraged her from using the opiates the surgeon had prescribed, and she survived on ibuprofen and acetaminophen for her first week at home. By the second week, she was fine. “I was lucky,” she told me. Her parents were doctors. They knew how to get her the specialists and tests she needed. Still, it took two years to figure this out. It must, she said, be so much harder for those without these advantages.

Lisa Sanders, M.D., is a contributing writer for the magazine. Her latest book is “Diagnosis: Solving the Most Baffling Medical Mysteries.” If you have a solved case to share, write her at Lisa.Sandersmdnyt@gmail.com.