Toxic synovitis occurs in children before puberty. It usually affects children from 2 to 12 years old. It is a type of inflammation of the hip. Its cause is not known. Boys are affected more often than girls. It can also occur after a common cold or viral infection.

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°F (38.33°C)
• Child only walking on toes and refusing to walk normally

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 (infection of the hip)
• Slipped capital femoral epiphysis (separation of the ball of the hip joint from the thigh bone, or femur)
• Legg-Calve-Perthes disease (disorder that occurs when the ball of the thigh bone in the hip does not get enough blood, causing the bone to die)

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. But, there is no danger with normal activities. Your child's health care provider may prescribe nonsteroidal anti-inflammatory drugs (NSAIDs) to reduce pain.

The hip pain goes away within 7 to 10 days.

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

Contact your child's provider for an appointment 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

Synovitis - toxic; Transient synovitis

Sankar WN, Winell JJ, Horn BD, Wells L. The hip. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 698.

Singer NG, Onel KB. Evaluation of children with rheumatologic complaints. In: Hochberg MC, Gravallese EM, Smolen JS, van der Heijde D, Weinblatt ME, Weisman MH, eds. Rheumatology. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 103.

Updated by: Neil K. Kaneshiro, MD, MHA, Clinical Professor of Pediatrics, University of Washington School of Medicine, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.