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

Synovitis - toxic; Transient synovitis

Toxic synovitis occurs in children before puberty begins. It is a type of arthritis of the hip. Its cause is not known, but boys are affected more often than girls (approximately 4 to 1).

Symptoms may include:

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

Aside from the hip discomfort, the child does not usually appear ill.

Toxic synovitis is diagnosed when other, more serious conditions have been ruled out, such as:

• Septic hip
• Slipped capital femoral epiphysis
• Legg-Calve-Perthes disease

Tests used to diagnose toxic synovitis include:

• Ultrasound of the hip
• X-ray of the hip
• ESR
• C-reactive protein (CRP)
• Complete blood count (CBC)

Other tests that may be done to rule out other causes of hip pain:

• 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 with performing normal activities. The health care provider may prescribe nonsteroidal anti-inflammatory medications (NSAIDS) 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 a fever
• Your child has been diagnosed with toxic synovitis and the hip pain lasts for longer than 10 days, the pain gets worse, or a high fever develops

Sankar WN, Horn BD, Wells L, Dormans JP. Transient monoarticular synovitis (toxic synovitis). In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 670.