As 4 year old Jimmy was getting ready for pre-school one morning, his mother noticed that he had a little bit of a limp. He told her his hip had an “owie”.   In recent days he had been healthy, but two weeks ago he had a cold. Mom recalled that he was walking fine last night and there wasn’t any history of falling or trauma. As the morning progressed, his limp seemed to worsen. It seemed odd to her that a child his age would have hip pain without some sort of injury. She decided to call his pediatrician.

What is transient toxic synovitis of the hip?

Sometimes referred to as “irritable hip”, transient toxic synovitis is a condition where there is inflammation of the inner lining of the hip joint. Transient toxic synovitis gets better on its own but because the hip joint can be irritated with infection or trauma, it’s important to evaluate the child for all these possibilities.

How common is this?

It usually presents itself between the ages of 3-10 and is the most common cause of sudden hip pain and limping in young children. Boys are affected 2-4 times more often than girls.

What causes transient toxic synovitis?

The exact cause is unknown. In approximately 30% of cases a viral infection or upper respiratory infection precedes the condition. This preceding illness may cause the body to overreact to a small strain of the hip that would otherwise have gone unnoticed. This may cause inflammation to the hip joint lining as a reaction. Trauma to the joint may also be a cause, but only 5% of cases have been reported just before the flare-up.

What are the typical symptoms?

Transient toxic synovitis causes pain in the hip, thigh, groin or knee on the affected side. There may be a limp (or abnormal crawling in infants) with or without pain. In small infants, there can be unexplained crying while changing a diaper. The condition is nearly always limited to one side. The pain and limp can range from mild to severe with the child refusing to move the hip or bear weight.

There can be a slightly raised temperature; higher fevers can point to other, more serious conditions. Children typically hold the hip slightly bent, turned outwards and away from the middle of their body.

How is transient toxic synovitis diagnosed?

To reach the diagnosis of transient toxic synovitis a number of other diagnoses need to be ruled out. Pain around the hip or limp in children can be due to a large number of conditions. Bacterial infection of the joint (septic arthritis), often presents with similar symptoms and thus plays a key role in evaluation. If left untreated, septic arthritis can quickly cause irreversible damage to the hip joint whereas transient toxic synovitis is believed to have no long-term consequences. Other hip problems that might cause similar symptoms include osteomyelitis, Legg-Calve-Perthes, and trauma.

Because of these multiple diagnoses, the work-up can proceed on many levels. For a child without fever who is still willing to bear weight, an x-ray and trial of anti-inflammatory medications may be sufficient. For children who appear more ill and who are unwilling to walk, blood work is often included. Uncommonly, an MRI may be necessary to thoroughly evaluate the structures about the hip. 

How is transient toxic synovitis treated?

Treatment consists of rest, and over-the-counter medications such as ibuprofen, followed by allowing the child to resume weight bearing as tolerated. Families should remain in contact with the child’s healthcare provider especially in instances of recurrence.

What is the long-term outlook?

This is a self-resolving condition that can last a few days. Once the inflammation begins to improve the symptoms will continue to decrease. Normal activities can be resumed as tolerated. There is a small chance of recurrence. Typically growth and function of the hip remains normal throughout life.

The pediatrician was reassured by Jimmy’s mother that trauma had not played a role. Because Jimmy was willing to bear some weight and because he had no fever, a course of children’s ibuprofen was started. The pediatrician had a phone consult with the pediatric orthopedic specialists at Rocky Mountain Pediatric OrthoONE who agreed that this conservative treatment was appropriate. Jimmy’s mother remained in contact with the pediatrician over the next several days as Jimmy began to resume his spunky 4-year old activities.