March 15, 2010 (New Orleans, Louisiana) — Almost half of children with fluid in the knee in the Northeastern United States are likely to have Lyme arthritis, according to a new study presented here at the American Association of Orthopaedic Surgeons 2010 Annual Meeting.

“In a pediatric population, Lyme arthritis is probably the first diagnosis to consider if you are in an endemic area,” Matthew D. Milewski, MD, from Yale–New Haven Children’s Hospital in Connecticut, told meeting attendees.

Connecticut has the highest rate of Lyme disease, but other areas of the United States are considered endemic, including the northeast from Maine to the mid-Atlantic states, Minnesota, Wisconsin and other Midwestern states, and Northern California.

Lyme arthritis is on the rise, increasing almost 100% in the past 15 years, according to data from the Centers of Disease Control and Prevention.

Children are nearly twice as likely to develop arthritis with Lyme disease than adults, and also to have it as the initial manifestation. Distinguishing children who have Lyme arthritis from those who have septic arthritis can be a challenge in the emergency department (ED), but doing so is essential because their treatment is so different, Dr. Milewski said.