Toxic synovitis is a condition affecting children that causes hip pain and limping.

Toxic synovitis is a frequent cause of limping with hip pain in children. It occurs in children prior to the onset of puberty and is a transient arthritis of the hip that usually resolves on its own. Its cause in not known but boys are affected more frequently than girls (approximately 4 to 1).

Symptoms are usually mild and generally include hip pain and a slight limp. The hip pain almost always involves only one side (unilateral). A low grade fever (usually less than 101 degrees) may be an early symptom. Aside from the hip discomfort, the child does not usually appear ill.

Toxic synovitis is a diagnosis of exclusion, which means that it is diagnosed when other, more serious conditions, have been ruled out. In children there are three potentially serious diseases that can cause hip pain and limp: septic hip, slipped capital femoral epiphysis, and Legg-Calve-Perthes disease. Once these other diagnoses have been excluded, then the diagnosis of toxic synovitis (which is the most common of all these diseases) is usually made.

Symptoms may include:

• Hip pain (on one side only)
• Limp
• Thigh pain, in front and toward the middle
• Knee pain
• Low grade fever, less than 101 degrees Fahrenheit

• Ultrasound of the hip
• X-ray of the hip
• ESR
• Complete blood count (CBC)

• Aspiration of fluid from the hip joint
• Bone scan
• MRI

Treatment often includes limiting activity to make the child more comfortable. However, there is no danger associated with performing normal activities. Nonsteroidal anti-inflammatory medications (NSAIDS) may be prescribed to reduce pain.

The hip pain goes away within 7 - 10 days.

Toxic synovitis goes away on its own. There are no expected long-term complications.

Call for an appointment with your child's health care provider if your child has unexplained hip pain or a limp, with or without associated fever.

If your child has a diagnosis of toxic synovitis you should call if the hip pain persists longer than 10 days, if the pain gets worse or if a high fever develops.

Hosalkar HS, Horn D, Friedman JE, Dormans JP. The Hip. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 18th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 677.