Acute Pediatric Leg Pain: Could Your Child Have Transient Synovitis Of The Hip?

We'd enjoyed a "slumber party", watching a film on my laptop in "the big bed", and my 10 year old daughter fell asleep just before the end. Not wanting to wake her, I let her be. The following morning, I woke up to quiet crying. My daughter. "What's wrong?", I asked. She replied, whimpering: "My leg hurts."

That was weird. She had suffered with "growing pains" before, but I knew that they always came at night, and that leg pain in the morning was cause for concern. It didn't end there, though — when she tried to get up, she found she couldn't walk. Pointing to where the pain was, she signalled an area from her knee all the way to her hip.

This was serious. A freak-out moment for both of us. Truly concerned, I called the doctor. Our pediatrician, based on the symptoms I described, suggested we see an orthopedic specialist instead of him. We did, and that specialist suggested an immediate x-ray after an initial physical examination, but wasn't too concerned.

What Is Transient Synovitis Of The Hip?

"I thought this is what she had," the orthopedic specialist told me after consulting his colleagues about my daughter's hip x-ray. "The way her hip moved suggested this, but I had to do an x-ray to be sure, because this condition is much more common in boys than in girls," he added.

She was diagnosed with transient synovitis of the hip, an inflammatory condition that causes the tissues around the hip joint to swell, leading to pain and impaired mobility. Only one side is usually affected, and children aged between three and 10 years old are most commonly struck by the condition. Besides restricted movement in the relevant hip joint and pain radiating out towards the thigh and even the knee, it can also cause a mildly raised temperature.

X-rays, physical examinations, and blood tests to rule out other conditions are involved in the diagnostic process.

What Causes Transient Synovitis Of The Hip?

Interestingly enough, our orthopedic specialist asked both whether my daughter had suffered a viral infection recently (she had) and whether she'd recently lost a milk tooth (she had, the night before she woke up in pain). That's because of the (as yet scientifically unsupported) theory that synovitis can occur as a complication of both these events. She had also been to sports practice the night before, another possible cause.

READ Hip Dysplasia - An Overview

In short, though the exact cause of transient synovitis of the hip hasn't yet been determined, what we do know is that it develops when the synovial membrane, the tissue around the hip joint, becomes inflamed — something the x-ray also clearly showed.

Transient Synovitis: Don't Panic, The 'Transient' Matters

When your child is suddenly limping or even unable to walk at all, that's really worrying — if it happens to your son or daughter, I fully assume that you'll have the same dark thoughts I had. (Thoughts that are not at all relieved by the fact that "leukemia" shows up as one of the answers to "causes of acute pediatric leg pain" if you use "Dr Google".)

Once you have a diagnosis of transient synovitis of the hip, though, there's good news. Although more serious conditions, such as Perthes disease and sceptic arthritis, have to be ruled out, the "transient" bit of the name of this condition means it will soon pass — and the treatment is much simpler than what you might have had in mind when you first noticed something was wrong with your child.

Treating Transient Synovitis Of The Hip

My daughter was ordered to be on complete bed rest (except for bathroom breaks) along with the use of the NSAID ibuprofen, to ease the pain and bring down the inflammation, for four days. That was boring to be sure, but not in the realm of "I'll never be able to walk again".

We went back for a checkup four days later, when she was already a bit better, and she was advised to stay in bed for four days longer. After eight days, we got the all-clear: we went from my daughter not being able to walk at all to her being fully functional again in just over a week, with the advice to come back after six months for a follow-up x-ray. This is because other hip conditions need to be ruled out, or treated if they are indeed present.

Recurrences can happen, but most children never experience the condition or related difficulties again: around 1.5% (yes, there's a period there) go on to develop recurring transient synovitis, Legg-Calvé-Perthes disease, Coxa magna, or osteoarthritis.

You may be advised to take your child swimming to strengthen the hip joint, and you may be told your child should refrain from playing other sports a few more weeks, but then you're most likely done, the experience to be relegated to the past.

READ 'Growing Pains' In Kids: Should You Be Worried?

The Bottom Line

In most cases, transient synovitis of the hip initially looks much scarier than it is in reality. Anything that can be completely cured with nothing but bed rest and over the counter anti-inflammatories is good news, no? Because several hip conditions that are indeed more serious are associated with transient synovitis of the hip (also called "irritable hip" in the UK), though, we can only advise you to diligently attend the follow-up appointments your doctor suggests.