Transient toxic synovitis of the hip

As 4-year-old Jimmy was getting ready for preschool 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 or "irritable hip"?

Sometimes referred to as "irritable hip," transient toxic synovitis is a condition in which the inner lining of the hip joint is inflamed. Transient toxic synovitis gets better on its own, but because the hip joint can be irritated with infection or trauma, it is important to evaluate the child for all possibilities. Transient Toxic Synovitis 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 are the causes of transient toxic synovitis?

The exact cause is not known. In about 30% of cases, a viral infection or upper respiratory infection happens before the symptoms of transient toxic synovitis appear. Illnesses such as these may cause the body to overreact to a small strain of the hip that would otherwise have gone unnoticed. This may cause inflammation (swelling) to the hip joint lining in 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 transient toxic synovitis 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 bodies.

How is transient toxic synovitis diagnosed?

To reach a 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 caused by a number of conditions. Bacterial infection of the joint (septic arthritis) often presents with similar symptoms and thus plays a key role in evaluation. If not treated, septic arthritis quickly can cause irreversible damage to the hip joint. On the other hand, transient toxic synovitis is believed to have no long-term effects. Other hip problems that might cause similar symptoms include osteomyelitis, Legg-Calve-Perthes, and trauma.

Because of the many possible causes of these symptoms, an evaluation may happen on many different levels. For a child without fever who is still willing to bear weight, an X-ray and trial of anti-inflammatory medications may be enough. For children who appear more ill and who are unwilling to walk, blood work is often included. Sometimes (but rarely), an MRI may be necessary to thoroughly look at the structures of the hip.

How is transient toxic synovitis treated?

A transient toxic synovitis treatment plan typically includes rest and over-the-counter medications, such as ibuprofen, followed by allowing the child to resume weight-bearing (for example, walking) as he/she can. Families should remain in contact with the child’s healthcare provider, especially if symptoms appear again.

What is the long-term outlook for transient toxic synovitis?

Transient toxic synovitis is a self-resolving condition that can last a few days; no medical interventions are necessary. Once the inflammation begins to improve, the symptoms will continue to lessen. The child can begin normal activities as soon as he/she would like. There is a small chance of it happening again, but typically growth and function of the hip remain normal throughout life.

Jimmy’s mother reassured the pediatrician 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 Hospital for Children who agreed that this conservative treatment was appropriate. Jimmy’s mother remained in contact with the pediatrician during the next several days as Jimmy began to resume his spunky 4-year-old activities.