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Q: My three-year-old son was diagnosed with toxic synovitis last month. He is now doing well, but I have not been able to find any literature on this condition. His doctor had none in his office and I have been searching the Web and have found nothing. Can you direct me to any info on this condition?
A: Toxic synovitis is an inflammation of the hip joint which occurs rather suddenly in young children. It is a very common cause of limp in early childhood. It occurs more in boys than in girls, and primarily affects children from 18 months to 5 years of age. The cause of toxic synovitis is not completely known, but it is felt to be a viral infection, or related to the body's immune response to a viral infection. It usually shows up as pain in the hip, severe enough to cause the child to limp, or refuse to walk. The hip's full range of motion is usually limited, so that a child doesn't want to turn the leg inward. It usually occurs in just one hip, but occasionally can occur on both sides at once.
Children usually do not have fever or other major symptoms associated with the hip pain in toxic synovitis. If xrays are taken of the hip, they are normal. The symptoms usually last for three or four days, and children get better with bedrest and ibuprofen within about a week. Most children have no further problem with the hip afterwards.
The reason that physicians get concerned when a child has this type of hip inflammation is that a more serious hip infection (septic arthritis, which needs to be treated with antibiotics), can sometimes be difficult to sort out from toxic synovitis. Most of the time children with a true septic arthritis are very sick, with high fevers, an extremely painful hip that can barely be moved, and some abnormal blood tests. Sometimes, however, it is not possible to tell the difference between the two just from the examination, and then the fluid in the joint has to be looked at. This is done by inserting a small needle into the joint and withdrawing some of the fluid. Further laboratory testing of the joint fluid can tell the difference between the two.
It sounds as though your son has recovered from his episode of toxic synovitis. It is rare but possible to have a second episode. There are no specific precautions that you need to take, other than routine visits with his primary health care provider.
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Shari Nethersole is a physician at Children's Hospital, Boston, and an instructor in Pediatrics at Harvard Medical School. She graduated from Yale University and Harvard Medical School, and did her internship and residency at Children's Hospital, Boston. As a pediatrician, she tries to work with parents to identify and address their concerns.