By Kate DaleyDec 16, 2019
Angela Angers’s daughter was two and a half years old when she woke up one morning and suddenly couldn’t walk.
"The night before she couldn't settle,” says Angers. “She was really uncomfortable and kept telling me that her legs hurt.” The next morning, her daughter had developed an obvious limp and wouldn’t put weight on her one leg. She reverted back to crawling to get around. Angers brought her daughter to see her doctor that day where she was diagnosed with transient synovitis.
Transient synovitis, also known as toxic synovitis, is inflammation in the hip joint, and commonly causes hip pain in children. While the science isn’t conclusive, doctors believe the inflammation is due to a virus or infection that occurs elsewhere in the body, causing an immune response. Then, either particles from the virus or a byproduct from the immune system’s reaction starts to migrate to the hip joint over a few weeks and causes inflammation of the joint lining that causes kids’ pain, explains Ran Goldman, a paediatrician and emergency physician at BC Children’s Hospital.
Transient synovitis usually causes pain in just one hip joint, but it can occur very rarely in both hip joints. Sometimes the pain starts gradually, causing a child to limp, and then potentially progressing until they won’t stand at all. Other times it comes on suddenly, as was the case with Angers’s daughter. In most cases, the child would have had a virus a few weeks prior and aren’t currently sick, though they could, in rare cases, have a low-grade fever.
Transient synovitis is not caused by any specific virus or infection—it could be anything from a gastrointestinal bug to an upper-respiratory infection. It’s seen most commonly after upper-respiratory infections, but that’s only because this is the most common infection, says Goldman.
Angers’s daughter had been experiencing the typical deluge of daycare viruses in the weeks leading up to the diagnosis but wasn’t currently sick or feverish when she had the hip pain and problems walking.
Toxic synovitis is most common in children between the ages of three and 10 years old, and boys are affected twice as often as girls. Goldman says it’s more common than people think—he sees about two to three children a week with this condition.
There’s a logical reason it’s so common. Most kids have 10 to 11 episodes of viral infections every year. “With so many infections in this age group, it is not surprising that we also see commonly transient synovitis [afterward], because this is kind of a remnant of the viral infection,” says Goldman.
“When I see children with hip pain and ask the parents, ‘Was your child sick two or three weeks ago?’ they're shocked and wonder how I know,’” says Goldman. A recent virus is a big hint for paediatricians.
Doctors rely on observation, medical history and a physical exam to make the final diagnosis.
Often, the doctor will find some resistance in the movement of the hip joint or the child won’t want to move it at all. No blood work or X-rays are necessary (transient synovitis doesn’t show up in those tests anyway).
“When I see children like this, we would give them ibuprofen and then we wait a little and we see that after an hour, the child will have much better movement with the leg and will be happier,” says Goldman.
Limping and pain in the legs or hip can be caused by many things, such as an injury, muscle strain or infection. “It’s important that parents go to see their doctor when a child is limping or not bearing weight, because it could be things other than transient synovitis,” says Goldman. “And it's important to differentiate between those.”
There is a chance it could be septic arthritis, a much more serious condition, where there are bacteria in the joint. If your child isn’t moving their legs at all, has a high fever (39 degrees Celsius or higher) or is generally unwell, see a doctor right away.
Transient synovitis is relatively benign, so any major changes in their condition should bring you right back to your doctor as well.
First, knowing that it’s not something serious means you can reassure your child that everything is OK, despite their scary or painful symptoms. Second, you can give your child a non-steroidal anti-inflammatory drug, like ibuprofen, to help them manage the pain. Third, encourage your child to rest and stick with a level of activity they can tolerate. Within two to seven days the toxic synovitis will disappear from the joint by itself, says Goldman.
Angers’s daughter stopped walking on the Monday and by the following Sunday, she was back to normal. “This really scary thing just kind of went away.” Her doctor told her to ensure that her daughter got lots of rest and to come back if she spiked a fever or had any additional symptoms. “Probably the most difficult part was—how do you keep a still toddler entertained,” says Angers. “There were a lot of movies and colouring going on for a couple of days.”
“This is a condition that is frightening in the beginning, but once it disappears, everyone forgets about it,” says Goldman. “It does not leave any long-term consequences.” But your child can get toxic synovitis more than once, he says. And some studies show that they actually might be more susceptible to it if they’ve had it once.
Though the experience was unsettling because she’d never even heard of this condition, Angers was just thankful her daughter’s hip pain wasn’t something more serious. “We went back to the doctor for a few more visits just to make sure, because I'm a first-time mom and I'm a bit overcautious, but she recovered just fine.”