Toxic Synovitis (Transient Synovitis)

Toxic synovitis is an inflammatory arthritis in the hip. It's the most common form of arthritis in children. Toxic synovitis comes on suddenly but goes away in a few days with no lasting effects. It's also called transient synovitis.

It usually occurs in children 3 to 10 years of age after a viral infection. It may be related to the body’s immune response to the virus. Many viral illnesses can trigger this response, including the common cold, stomach flu, chickenpox, mumps, rubella, and other contagious diseases.

Toxic synovitis usually causes a limp and hip, thigh, or knee pain. Usually only one hip is affected. But sometimes both hips are involved. There is usually no fever, redness, or swelling of the joint. It's not a contagious disease. The healthcare provider may order blood tests or X-rays to rule out other causes of hip pain.

Home care

Walking will hurt for the next few days. Your child should stay home and rest as long as they have a limp.

You may give over-the-counter medicine as directed based on age and weight for fever, fussiness, or discomfort. In infants older than 6 months of age, you may give a non-steroidal anti-inflammatory medicine such as ibuprofen. This medicine may help better than acetaminophen. Talk with your child's healthcare provider before giving these medicines if your child has chronic liver or kidney disease. Also talk with the provider if your child has had a stomach ulcer or digestive bleeding. Never give aspirin to a child under 18 years of age who is ill with a fever. It may cause severe disease (Reye syndrome) or death.

Follow-up care

Follow up with your child's healthcare provider, or as advised.

When to get medical advice

Call your child's healthcare provider right away if any of these occur:

  • Pain or limp that gets worse or doesn't go away after 3 or 4  days

  • Pain in other joints

  • Rash

  • Fever (see "Fever and children" below)

Fever and children

Use a digital thermometer to check your child’s temperature. Don’t use a mercury thermometer. There are different kinds and uses of digital thermometers. They include:

  • Rectal. For children younger than 3 years, a rectal temperature is the most accurate.

  • Forehead (temporal). This works for children age 3 months and older. If a child under 3 months old has signs of illness, this can be used for a first pass. The provider may want to confirm with a rectal temperature.

  • Ear (tympanic). Ear temperatures are accurate after 6 months of age, but not before.

  • Armpit (axillary). This is the least reliable but may be used for a first pass to check a child of any age with signs of illness. The provider may want to confirm with a rectal temperature.

  • Mouth (oral). Don’t use a thermometer in your child’s mouth until they are at least 4 years old.

Use the rectal thermometer with care. Follow the product maker’s directions for correct use. Insert it gently. Label it and make sure it’s not used in the mouth. It may pass on germs from the stool. If you don’t feel OK using a rectal thermometer, ask the healthcare provider what type to use instead. When you talk with any healthcare provider about your child’s fever, tell them which type you used.

Below are guidelines to know if your young child has a fever. Your child’s healthcare provider may give you different numbers for your child. Follow your provider’s specific instructions.

Fever readings for a baby under 3 months old:

  • First, ask your child’s healthcare provider how you should take the temperature.

  • Rectal or forehead: 100.4°F (38°C) or higher

  • Armpit: 99°F (37.2°C) or higher

Fever readings for a child age 3 months to 36 months (3 years):

  • Rectal, forehead, or ear: 102°F (38.9°C) or higher

  • Armpit: 101°F (38.3°C) or higher

Call the healthcare provider in these cases:

  • Repeated temperature of 104°F (40°C) or higher in a child of any age

  • Fever of 100.4° F (38° C) or higher in baby younger than 3 months

  • Fever that lasts more than 24 hours in a child under age 2

  • Fever that lasts for 3 days in a child age 2 or older

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