What Is Toxic Synovitis?

Medically Reviewed by Dany Paul Baby, MD on April 20, 2022
4 min read

Toxic synovitis may sound scary, but it is usually no cause for worry. It is a temporary joint condition that affects children. It occurs due to the inflammation or swelling of the hip joint and causes hip pain and limping in children. It is also known as transient synovitis.

The synovium or synovial membrane is the connective tissue in your joints, like the knees, hips, and ankles. When there's inflammation or swelling in the synovium, it's called synovitis.

If synovitis occurs in the hip joint in children, it is called toxic synovitis. It is also called transient synovitis because it is a temporary condition. It causes swelling or inflammation of the hip, pain in the hip and leg, and limping. Your child may feel uncomfortable and unsettled, as these symptoms start suddenly. 

However, there’s no need to worry because transient synovitis usually goes away in a week or two. Also, it doesn’t cause any long-term health problems or complications.

Toxic synovitis can happen at any age, but it is commonly seen in children ages 3 through 10. It affects boys more often than girls. It also affects the right side of the hip more often.

Toxic synovitis causes are unknown. However, certain risk factors can increase your child's chances of developing the condition. These include:

  1. Viral infections. During a viral infection like a cold or stomach infection, the immune system makes substances to fight the virus. Doctors believe these substances can cause inflammation and lead to toxic synovitis. 
  2. Bacterial infections. Certain bacteria such as Streptococcus can increase the risk of toxic synovitis in children. In this case, it is called post-streptococcal toxic synovitis.
  3. Upper respiratory infections.Upper respiratory infections like those that cause a cough or sore throat can increase the risk of toxic synovitis.
  4. Injury or trauma. If your child has previous injury or trauma, they may have inflammation. This can increase their chances of developing toxic synovitis.

Sudden inflammation in the hip joint can cause hip or leg pain, which can make your child uncomfortable. Transient synovitis symptoms include:

  • Hip pain on only one side, usually the right side
  • Hip discomfort after sitting in one place for too long
  • Limping
  • Walking on tiptoes
  • Thigh pain, in the front and middle of the thigh
  • Knee pain
  • Low-grade fever, below 101 degrees Fahrenheit or 38.33 degrees Celsius

Look out for symptoms of a recent viral infection like a cold or stomach infection. Also, check for trauma or injury, which may cause inflammation in the hip joint. These can be important signs of toxic synovitis.

If your child develops toxic synovitis, hip or leg pain appears suddenly. They may cry and refuse to walk. Apart from this, your child won’t seem to be ill. In younger children and babies, transient synovitis symptoms include abnormal crawling and crying. Children may even cry when the hip joint is moved during activities like changing their diaper.

Toxic synovitis diagnosis mainly involves a physical exam. The doctor will examine whether your child’s knee, hip, and leg joints hurt during movement. This helps the doctor check if your child is limping because of hip joint pain.

The doctor may use imaging tests like ultrasound or MRI to check for swelling or inflammation in the hip joint. They may order blood tests to confirm the condition. They may also remove some joint fluid using a needle to check for inflammation.

Transient synovitis symptoms can resemble symptoms of other serious joint conditions, such as: 

  • Septic arthritis. Septic arthritis or infectious arthritis occurs when a bacterial infection affects the joints, leading to long-term damage. 
  • Slipped capital femoral epiphysis. Slipped capital femoral epiphysis is when the hip joint separates from the thigh bone, which can be very painful. 
  • Legg-Calve-Perthes disease. Legg-Calve-Perthes disease is when the part of the thigh bone that connects to the hip doesn’t get enough blood. This can cause the bone to weaken and die.

 These conditions can easily be ruled out through a physical exam and other diagnostic tests.

Toxic synovitis treatment includes anti-inflammatory drugs to reduce swelling in the hip. The doctor may prescribe nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen for four weeks. They may also prescribe pain medication such as acetaminophen to manage hip and leg pain.

Too much activity can put pressure on the hip joint and worsen the pain. So, the doctor may ask your child to reduce activity. This helps rest the hip joint, ease the pain, and improve recovery. Your child can walk comfortably within one or two days of taking medicines. However, it’s best to avoid strenuous exercise and sports till they fully recover.

Toxic synovitis can’t be prevented, but it is temporary and treatable. Toxic synovitis usually goes away within one or two weeks after treatment. But if you don’t take care, symptoms can last for four or five weeks. 

Your doctor will ask you to bring your child for a follow-up after a few weeks of treatment. This is important to ensure that the symptoms have gone away. If your child still has symptoms or some stiffness in the hip joint, the doctor may order imaging tests to check again.

Toxic synovitis usually goes away on its own. It doesn’t have any long-term complications. The only problem is that toxic synovitis can occur multiple times if proper care is not taken. So, it is important to follow the doctor's instructions to heal completely. Also, let your doctor know if your child has a history of toxic synovitis, injury, or trauma.

Toxic synovitis is not a serious condition. However, consult your doctor immediately if your child has any of the following:

  • Unexplained hip pain, leg pain, or limping, with or without a fever
  • A toxic synovitis diagnosis with hip pain for more than 10 days
  • Worsening hip or leg pain after diagnosis
  • High fever 

Early diagnosis and treatment can help prevent the condition from worsening.