Transient synovitis (sin-uh-VEYE-tis) is inflammation of one or both hips that mostly affects kids younger than 10 years old. The hip joint gets extra fluid in it and a swollen lining. This causes hip pain and limited movement of the joint, so kids who have it might walk with a limp.

Transient synovitis usually doesn't cause long-term problems, and most kids feel better within 7–10 days. Sometimes it can take a few weeks for symptoms to completely go away.

• If your child is uncomfortable, and your health care provider says it's OK, you can give medicines such as:
  • ibuprofen (such as Advil^®, Motrin^®, or a store brand). Don't give ibuprofen to babies under 6 months old. 
  • acetaminophen (such as Tylenol^® or a store brand) 

Follow the package directions for how much to give and how often. If you don't know the recommended dosage or your child is younger than 2 years old, call your health care provider. 

• Help your child rest while recovering.
• Your child can return to walking or crawling as soon as they feel comfortable enough to do so.
• Your child can return to all other normal activities (like gym and sports) when the pain is completely gone and there is no limp.

Your child:

• has a new fever above 101°F (38.3°C)
• has pain that gets worse or is not controlled by medicine
• develops pain in other joints
• still has pain after 10 days

• Your child can't move the affected joint.
• The skin around the hip becomes red or swollen.

How do kids get transient synovitis? Experts don't know the exact cause of transient synovitis (also called "toxic synovitis"). Often, it happens after a child has a cold or diarrhea illness, so it might happen because the body's immune system was fighting an infection.

How is transient synovitis diagnosed? Health care providers will check for transient synovitis when a child has pain in one or both hips, pain in the knee or thigh, or a limp. After doing an exam, they'll order some tests, such as an ultrasound and blood tests. Sometimes testing on the fluid in the hip joint is needed. After making sure there isn't a more serious cause of the hip pain, they can make the diagnosis of transient synovitis.

Can my child get transient synovitis again? Yes. Kids who get transient synovitis may get it again during childhood. If your child has hip or leg pain, or gets a limp again, tell their health care provider that they've had transient synovitis before.