Toxic synovitis, also called transient synovitis or irritable hip, is a condition that causes inflammation and pain in the hip. It primarily affects children.

A child with toxic synovitis may limp, complain of hip and leg pain, or otherwise be reluctant to walk. The condition is not contagious and usually clears up within 2 weeks.

In this article, learn more about the symptoms of toxic synovitis. We also look into the treatment options and whether it can occur in adults.

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Toxic synovitis usually affects the hip joints.

Toxic or transient synovitis is a temporary condition that causes pain and inflammation of a joint, almost always in the hip. It usually affects children.

Although symptoms can start suddenly and alarm caregivers, toxic synovitis typically clears up within 1–2 weeks. Some cases last as long as 5 weeks. It does not usually cause any long-term complications.

Toxic synovitis primarily affects children, and it may also occur in adults. However, adult cases are rare and have not been documented well. It is more likely that these adults developed septic arthritis, which can be confused with toxic synovitis.

Septic arthritis can cause similar pain in the hip joint. However, bacterial infection causes this condition, and it can lead to permanent damage if a person does not receive treatment.

The condition is most common in children between the ages of 3 and 8. It can occur at any age, but it is very unlikely to appear in adults.

Toxic synovitis is more prevalent in boys than girls.

The most common symptom is the sudden occurrence of hip or leg pain on one side of the body. The pain typically causes a limp.

Other symptoms of toxic synovitis include:

  • walking on tiptoes
  • unintentionally turning the legs out
  • crying (in young children)
  • a low-grade fever
  • complaining about hip discomfort after sitting or resting for a long time
  • having a recent viral infection
  • having pain with walking
  • not wanting to walk
  • having pain in knee or thigh

In infants, the signs may include:

  • crying when moving the hips
  • abnormal crawling
  • unexplained crying

Toxic synovitis is unlikely to occur in adults, but they can develop septic arthritis. This primarily causes pain and swelling in a single joint, possibly in the knee, elbow, or hip.

Additional symptoms of septic arthritis include:

  • redness and swelling in the joint
  • intense pain in the joint
  • loss of mobility in the joint
  • fever and chills
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Toxic synovitis often occurs after a viral infection.

Doctors are still uncertain about the exact cause of toxic synovitis, but it often occurs following a viral infection, such as those that cause diarrhea or a cold.

Because of this, there is a suspicion that the child’s immune system creates something while fighting the infection that then causes toxic synovitis.

In cases of septic arthritis, a person develops joint pain following bacterial or fungal infection. The infection often spreads to the joint from another part of the body.

Toxic synovitis can be difficult to diagnose because a doctor must first rule out other conditions. Conditions with similar symptoms include:

  • septic arthritis
  • slipped capital femoral epiphysis (SCFE)
  • Legg-Calvé-Perthes disease, which causes insufficient oxygen to reach the hip, leading to its collapse
  • unrecognized trauma or musculoskeletal pain

A doctor usually asks about the child’s symptoms, then conducts a physical examination. During this, they move the joints of the legs around, to confirm the location of the pain.

A doctor may also order an ultrasound of the hip. This allows them to look for inflammation and fluid in the joint.

A blood test can show the extent of swelling and some signs of bacterial infection. An X-ray can help the doctor to rule out both SCFE and Legg-Calvé-Perthes disease.

Diagnosing adults

A doctor conducts a physical examination. To rule out septic arthritis, they may also take a sample of fluid from the joint.

The doctor will also take a culture sample to check for bacteria that indicate septic arthritis.

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A doctor may prescribe anti-inflammatory medication to treat toxic synovitis.

Rest is a crucial part of treating toxic synovitis. A child should avoid strenuous physical activity and try not to move around too much when diagnosed.

A doctor will likely prescribe or recommend anti-inflammatory medications, such as ibuprofen and naproxen. These can reduce the inflammation in the joint, helping the child to walk more comfortably.

Over-the-counter medications are often sufficient, but if the child continues to experience discomfort, the doctor may prescribe a stronger dosage.

A child should fully recover within 1–2 weeks. In some cases, it may take up to 5 weeks. While recovering, a child should avoid strenuous activities, including physical activity during recess, after-school sports, and gym class.

If symptoms do not clear up, return to the doctor. They may need to run additional tests and rule out other conditions.

Toxic synovitis causes no long-term complications. However, some children develop it multiple times.

Authors of one review found that the recurrence rate for toxic synovitis was 0–26 percent in their sample of studies.

A child with toxic synovitis who receives basic treatment will usually make a full recovery within 2 weeks.

It is essential to see a doctor for a proper diagnosis so that they can rule out more serious conditions. This is an especially good idea if the child:

  • is younger than 3 or older than 8
  • has a high fever
  • refuses to walk
  • otherwise appears to be ill

Adults are unlikely to develop toxic synovitis. They can develop septic arthritis, which feels similar. This condition can be severe and lead to permanent damage if a person does not receive treatment.