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The Informed Parent

Young Boy With A Limp — Toxic Synovitis

by Louis P. Theriot, M.D., F.A.A.P.
Published on Jun. 28, 2010

A.J., a three-year-old boy, was brought to the office because of a limp. He was perfectly healthy yesterday until he awoke from his afternoon nap. Mother said that he seemed a bit fussy and refused to bear any weight. “It was so odd,” she said. “He was just fine when I put him down for his nap.”

She said that he wouldn’t fully straighten out his leg and held it partially flexed. When he did try to walk he had a limp. His temperature was 99.1 degrees, but he didn’t have any other symptoms. She gave him Tylenol and encouraged him to rest. However this was not an easy task as he still wanted to play and be active. After talking it over with her husband and her mother they felt he must have sprained his leg as he is an active child. But she wasn’t totally convinced because there was absolutely no history of recent trauma. They decided if it wasn’t better in the morning she would make an appointment.

Although he had a fitful night he slept OK. In the morning, getting out of bed, he fell to the floor as his left leg gave out. He cried in pain. Again he kept his leg partially flexed and didn’t want to try to stand.

When I saw him in the office his temperature was 98.9 degrees and his vital signs were normal. I could not elicit any further history of trauma or a fall. His exam was completely normal except for the left lower extremity.

First of all, there was no swelling or redness anywhere along the leg. The left leg was perfectly symmetrical to the right leg. Laying on his back he did prefer to have the left leg partially bent at the knee. When I slowly tried to straighten it out he winced and resisted as it obviously was uncomfortable.

I assumed the problem was in the hip so I started at the foot and ankle and worked my way up to the hip. There was no foreign body or cut on the bottom of his foot. His ankle joint had full range of motion and there was no swelling or tenderness. The same was true for the left knee. When I tried to range his hip, he resisted saying it hurt, and clearly there was a decreased range of motion.

Now we have a three-year-old with a hip problem, no fever to speak of, and no history of trauma. The possibilities include an infection of the hip which is a medical emergency, a sprain or soft tissue injury, or toxic synovitis. As a bacterial infection in the hip is a medical emergency I wanted to rule this out as quickly as possible. He was sent to an imaging center for an ultrasound of the hip, and to the lab for some blood work. Mom was told to bring him back to the office after this was done. A few hours later he was seen again. At this time his temperature was 98.6 degrees and his exam was virtually unchanged.

The lab work came back. The white blood count was normal as was his CRP, which is a non-specific marker for inflammation. If he truly had a bacterial infection of the hip ( a septic hip) the white count should have been high as well as the CRP. This was reassuring. The ultrasound of the hip was also read as normal. Speaking with the radiologist, he indicated there might be a tad bit more fluid in the left hip joint, but certainly not consistent with a septic joint. This too was reassuring.

Given all of this information I told mom that I thought he had a condition called toxic synovitis. It is presumed to be a viral infection of the hip that is seen in children usually between three and eight years of age. It is 2-to-4 times more likely to affect boys than girls. It is a self-limiting infection that resolves with time and conservative measures. If allowed to heal properly it should cause no long-term effects or issues.

Mom was instructed to give him Ibuprofen instead of Tylenol because of it’s anti-inflammatory properties. He was to limit his activity to bed rest with no weight bearing. I also wanted to see him back the next day.

The following day he still was without fever and now could straighten out his leg comfortably. He still wanted to favor his leg when he walked, but overall he was markedly improved. Mom was to continue doing the same things and I would see him again the next day before the weekend.

On this visit he came in as a different child. He had no pain whatsoever. So anxious to show me how much better he was, I was greeted walking in the door with him standing on the examining table. ”Hey, Dr. T. Watch this!” And he jumped off the table onto the floor. No doubt he was back to normal. I told mom that for the weekend I wanted her to limit his activity to walking, but no running or jumping. She could now give the Ibuprofen on an as needed basis. She was to call on Monday with an update. When the call came in she was begging to let him return to full activity as he was driving her nuts trying to keep him from running.

When evaluating a young child for a limp, it is critical to be sure that one is not dealing with a septic hip. This is a medical emergency  as the infection can literally destroy the joint if not treated as soon as possible. The treatment in most cases is surgical drainage, requiring an orthopedic surgeon. And time is of the essence. Antibiotics are important as well. In addition to the surgery the duration of antibiotics may be as long as 4-to-6 weeks. Usually a child with a septic hip will have fever, a high white blood count, an elevated CRP and an abnormal ultrasound showing fluid in the joint space. But it can not be stressed enough that a septic hip MUST BE RULED OUT WITHOUT QUESTION!

A sprain is also a common cause of a limp in a child, particularly an active one. Often times however, the parent cannot recall a particular fall or injury. These children also do not have fever and their exam is more vague. The examiner cannot localize pain or limitation of a particular joint. There is no swelling or redness. If labs are done they too would be normal. This should resolve over a few days.

When evaluating a child with a limp, one must think of the obvious such as a foreign body in the foot, a plantar wart on the ball of the foot or the big toe, or something as silly as a stone or sharp object in the shoe. (“He only limps when he is wearing his shoes“).

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