Lyme disease’s early knee effusion is different from septic arthritis in children. Septic arthritis and knee effusions seen in Lyme disease share similar symptoms in children, but do require different treatment options. That’s why it’s so important to recognize the differences in order to ensure the treatment is appropriate for the condition.
Septic arthritis requires emergency surgical irrigation and drainage to prevent irreversible damage. Lyme disease is an infection caused by tick bites, which transmit bacteria normally found in deers. Treatment for Lyme disease is typically a regime of antibiotics.
In the study, researchers reviewed medical records of 189 patients under the age of 18 with excess fluid in the knee. Of these patients, 23 had culture-positive septic arthritis, 26 had culture-negative septic arthritis, and 140 had Lyme disease.
The researchers outlined four characteristics that are predictive of septic arthritis. These characteristics are: knee pain with short range of motion, C-reactive protein of less than 4.0 mg/L, fever, and age group under two years old.
Study author Dr. Wudbhav N. Sankar said, “The probability of septic arthritis with any one factor present was 18 percent, compared to 100 percent will all four factors present. Our study offers a useful prediction algorithm to help distinguish septic arthritis from a knee effusion caused by Lyme disease in children.”
An alternative study found that it is far more common for children to develop Lyme disease arthritis than septic arthritis in high-risk Lyme disease areas. Researcher Dr. Matthew D. Milewski said, “In a pediatric population, Lyme arthritis is probably the first diagnosis to consider if you are in an endemic area.”
“In Connecticut, where Lyme disease is endemic, a lot of kids would come into our emergency department with a swollen joint, and we would be forced to try to decide whether this person had septic arthritis or Lyme arthritis. Septic arthritis is traditionally considered a surgical indication in most cases, and Lyme arthritis is considered something that can be treated with antibiotics. This is a big difference in treatment options, and we wanted to help the providers in the emergency department try to decide between these two courses of treatment,” added Dr. Milewski.
The researchers conducted a retrospective review of all joint aspirations in children younger than 18. They collected data on cell counts, fluid differentials, culture, hematologic inflammatory markers (including peripheral white blood cell count, peripheral blood differential, erythrocyte sedimentation rate, and C-reactive protein), and Lyme disease serological testing.
The researchers analyzed 391 children. Thirty-one percent tested positive for Lyme disease and 13 percent had septic arthritis.
Dr. Milewski explained, “We don’t have a rapid Lyme test that helps the care provider at the point of initial presentation to decide if this is Lyme or not, but this information gives us a way to start to lean a practitioner one way or the other if they are on the fence. It speaks to the fact that Lyme disease is so common that it really needs to be considered every time you evaluate a kid for septic arthritis.”