Lyme or Arthritis?  A new study in the May 4 issue of the Journal of Bone and Joint Surgery reviewed the records of 189 patients under age 18 who presented to Children’s Hospital of Philadelphia (CHOP) with excess fluid in the knee between 2005 and 2013. Of these patients, 23 had culture-positive septic arthritis; 26, culture-negative septic arthritis; and 140, Lyme disease or 74% of the total children included.

It also identified four symptoms that are predictive of septic arthritis, which is considered a medical emergency requiring surgical irrigation (flushing) and drainage to prevent rapid and irreversible destruction of the cartilage surrounding the knee.

Knee pain with a short range of motion
A C-reactive protein (CRP test; used to measure inflammation) of >4.0 mg/L
Age younger than 2

“The probability of septic arthritis with any one factor present was 18 percent compared to 100 percent will all four factors present,” said study author Wudbhav N. Sankar, MD, an orthopaedic surgeon at Children’s Hospital of Philadelphia. “Our study offers a useful prediction algorithm to help distinguish septic arthritis from a knee effusion caused by Lyme disease in children.”

Lyme disease, on the other other-hand, is treated with antibiotics.  In addition to knee swelling and pain, both conditions may cause a fever, swelling of other joints, irritability and an inability to bear weight on the affected extremity. Common laboratory tests to measure inflammation, as well as white blood cell counts, also may be elevated.

It would be prudent to take the child through various checklists as MSIDS (multi systemic infectious disease syndrome or Lyme with friends) is a clinical diagnosis as the tests often come back negative for Lyme (borrelia) as well as the various coinfections; however, children are often not perceptive about what they are feeling physically in their body and/or they have a difficult time relaying verbally.  This is where parents need to be their child’s advocate, do the reading and understand the concepts, and fight for your child.  A person’s chances are always better if MSIDS is caught early.


For an excellent article on LD in children:

Also, a book about when your child has LD:



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