Transient synovitis - also known as toxic synovitis - is a painful inflammation of the inner lining (synovium) of the hip joint and surrounding area. This condition occurs mostly in children between the ages of 3 and 10 and is seen more often in boys. The condition usually lasts only for a short time, hence the name “transient.”

Children with transient synovitis may limp, with toes turned outward. The knee might be straight or bent, and the child may tiptoe while walking – or refuse to walk at all due to pain. The child may also have pain in the thigh and knee and a fever of up to 101° F.

In transient synovitis, hip discomfort usually shows up after the child sits in the same position for a long time. It usually occurs in just one hip, but can sometimes affect both hips. Babies affected with transient synovitis may cry during diaper changes or times when their hip joints are moved.

There is no exact known cause of transient synovitis, only theories.  Doctors are not certain whether it is due to a viral infection in the hip joint, or perhaps a type of allergic reaction to a virus somewhere else in the body.

Transient synovitis is often confused with septic arthritis, a more serious and longer-lasting condition caused by a bacterial infection in the hip joint.

Since there is no known cause of transient synovitis, it really is a “diagnosis of exclusion,” the result of eliminating other possible causes of hip pain in the child.

First, the doctor conducts a physical examination, moving the knee, hip, and other joints to determine if the pain really is coming from the hip joint. The doctor may also use ultrasound to determine if there is fluid (effusion) in the hip joint, which may or may not mean synovitis. An X-ray of the hip, bone scan, or even an MRI may also be used. Again, these tests are done to eliminate other causes of hip pain.

Blood tests like the ESR (erythrocyte sedimentation rate) can sometimes find signs, or “markers,” of infection. As with the other testing, these are performed to rule out other possible causes of the patient’s pain, such as septic arthritis, osteomyelitis (infection of bone tissue), fractures, and joint/bone defects. A sample of fluid may be taken from the hip, to provide as much of a complete picture of the patient’s health as possible.

The most common treatment for transient synovitis is nonsteroidal anti-inflammatory drugs such as ibuprofen to relieve pain, and non-weight bearing rest. Doctors advise that the child’s temperature be checked often, and any temperature over 99°F reported.

Getting an otherwise healthy child to “lie down and stay down” might be a chore, but often they can recover in 7 to 10 days and then resume their normal level of activity. (Some doctors may follow up in a few months time with an X-ray to check the condition of the hip joint.)

Treatment for transient synovitis sounds simple enough, but it is still important to call your doctor if your child is experiencing hip pain. While transient synovitis is not serious, other causes of hip pain can be very serious – and only your doctor can make the diagnosis.

If your child has been diagnosed with transient synovitis, and the pain and swelling continue after ten days, contact your doctor’s office. Or, if the child develops a high fever and the pain gets worse, call your doctor immediately as this could be a sign of septic arthritis, a very serious condition.

Outlook

Generally transient synovitis can go away in a week’s time, but it can sometimes linger for more than four weeks. If a child develops a cold or other viral infection, the virus can travel to the hip joint and stay there, resulting in repeated bouts of transient synovitis throughout childhood. Any time your child’s symptoms “rebound,” contact your doctor right away.