December 2013-  Over twice as many children had Lyme related arthritis affecting the knee than both septic arthritis and "other" causes of arthritis combined.  And that was based on having to have a positive Lyme test!

"We identified 384 children with knee monoarthritis, of whom 19 (5%) had septic arthritis, 257 (67%) had Lyme arthritis and 108 (28%) had other inflammatory arthritis."

From the *Division of Emergency Medicine, Boston Children's Hospital; †Harvard Medical School, Boston, MA; ‡Johns Hopkins Medical School and Johns Hopkins Children's Center Baltimore, MD; ∥Division of Immunology, Boston Children's Hospital; §Division of Rheumatology, Immunology and Allergy, Brigham and Women's Hospital, Boston, MA; ¶Department of Orthopedics and Rehabilitation, Yale University School of Medicine, New Haven; and #Elite Sports Medicine, Connecticut Children's Medical Center, Farmington, CT; and **University of Melbourne School of Medicine, Melbourne, Australia.

Pediatr Emerg Care. 2013 Dec 20. [Epub ahead of print]
Synovial Fluid Findings in Children With Knee Monoarthritis in Lyme Disease Endemic Areas.

Deanehan JK, Nigrovic PA, Milewski MD, Tan Tanny SP, Kimia AA, Smith BG, Nigrovic LE.
Author information


Although Lyme and septic arthritis of the knee may have similar clinical presentations, septic arthritis requires prompt identification and treatment to avoid joint destruction. We sought to determine whether synovial fluid cell counts alone can discriminate between Lyme, septic, and other inflammatory arthritis.

We conducted a retrospective cohort study of children aged 1 to 18 years with knee monoarthritis who presented to 1 of 2 pediatric emergency departments located in Lyme endemic areas. We included children who had both a synovial fluid culture and an evaluation for Lyme disease. 

Septic arthritis was defined as a positive synovial fluid culture or synovial fluid pleocytosis (white blood cell [WBC] ≥40,000 cells/μL) with a positive blood culture. Lyme arthritis was defined as positive Lyme serology without a positive bacterial culture. 

All other children were considered to have other inflammatory arthritis. We compared the synovial fluid counts by arthritis type.

We identified 384 children with knee monoarthritis, of whom 19 (5%) had septic arthritis, 257 (67%) had Lyme arthritis and 108 (28%) had other inflammatory arthritis. 

Children with other inflammatory arthritis had lower synovial WBC and absolute neutrophil count, as well as percent neutrophils, than those with either Lyme or septic arthritis. 

There were no significant differences in the synovial fluid WBC, absolute neutrophil count, and percent neutrophils for children with Lyme and septic arthritis.

In Lyme endemic areas, synovial fluid results alone do not differentiate septic from Lyme arthritis. Therefore, other clinical or laboratory indicators are needed to direct the care of patients with knee monoarthritis.

PMID: 24365728 [PubMed - as supplied by publisher]


Arthritis Rheum. 1977 Jan-Feb;20(1):7-17.

Lyme arthritis: an epidemic of oligoarticular arthritis in children and adults in three connecticut communities.


An epidemic form of arthritis has been occurring in eastern Connecticut at least since 1972, with the peak incidence of new cases in the summer and early fall. Its identification has been possible because of tight geographic clustering in some areas, and because of a characteristic preceding skin lesion in some patients. The authors studied 51 residents of three contiguous Connecticut communities -- 39 children and 12 adults -- who developed an illness characterized by recurrent attacks of asymmetric swelling and pain in a few large joints, especially the knee. Attacks were usually short (median: 1 week) with much longer intervening periods of complete remission (median: 2.5 months), but some attacks lasted for months. 
To date the typical patient has had three recurrences, but 16 patients have had none. A median of 4 weeks (range: 1-24) before the onset of arthritis, 13 patients (25%) noted an erythematous papule that developed into an expanding, red, annular lesion, as much as 50 cm in diameter. Only 2 of 159 family members of patients had such a lesion and did not develop arthritis (P less than 0.000001). 
The overalll prevalence of the arthritis was 4.3 cases per 1,000 residents, but the prevalence among children living on four roads was 1 in 10. Six families had more than 1 affected member. Nine of 20 symptomatic patients had low serum C3 levels, compared to none of 31 asymptomatic patients (P less than 0.005); no patient had iridocyclitis or a positive test for antinuclear antibodies. Neither cultures of synovium and synovial fluid nor serologic tests were positive for agents known to cause arthritis. "Lynne arthritis" is thought to be a previously unrecognized clinical entity, the epidemiology of which suggests transmission by an arthropod vector.
PMID: 836338 [PubMed - indexed for MEDLINE]

Long-Term Course of Arthritis in Children


From Medscape Medical News

Pediatric Lyme Arthritis Twice as Common as Septic Arthritis in Endemic Areas of Lyme Disease

Fran Lowry

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.

"In Connecticut, where Lyme disease is endemic, a lot of kids would come into our [ED] with a swollen joint, and we would be forced to try to decide whether this person had septic arthritis or Lyme arthritis," Dr. Milewski told Medscape Orthopaedics. "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 [ED] try to decide between these 2 courses of treatment."

In their study, Dr. Milewski and colleagues sought to determine how often children presented with Lyme arthritis at their center, and how they differed from children with septic arthritis.

They undertook a retrospective review of all joint aspirations done from January 1992 to April 2009 in children younger than 18 years. They collected data on cell count, fluid differential, 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.

They also reviewed charts for the presence of fever and weight-bearing status at the time the children presented, and for radiographic or ultrasound evidence of effusion.

Of the 391 patients who were analyzed, 123 (31%) tested positive for Lyme disease and 51 (13%) had septic arthritis.

They also found that children with septic arthritis had a higher nucleated cell count than those with Lyme arthritis (123,000 vs 60,200 cells/mm; P = .007).

They were also more likely to have fever. Twenty-seven of 49 septic arthritis patients (55%) had temperatures of at least 101.5 °F, as did 26 of 120 Lyme patients (22%); 33 of 49 septic arthritis patients (67%) had a low-grade fever, defined as a temperature of at least 100.4 °F, as did 46 of 120 Lyme patients (38%).

Both of these temperature cut-offs were found to be significantly different between the 2 cohorts (P < .001 and 0.001, respectively).

In addition, virtually all of the children with septic arthritis refused to bear weight, compared with only 39% of the children with Lyme arthritis (< .001).

Erythrocyte sedimentation rate and C-reactive protein values were similar in the 2 groups and did not help to distinguish between them, Dr. Milewski noted.

This study gives providers more tools to help determine their course of treatment, Dr. Milewski told Medscape Orthopaedics.

"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."

Commenting on this study for Medscape Orthopaedics, Theodore J. Ganley, MD, director of sports medicine at the Children's Hospital of Philadelphia and associate professor at the University of Pennsylvania School of Medicine in Philadelphia, agreed. "The emphasis from this study is that if you have a child with a mild injury and you have a significant knee effusion that is atraumatic or with minimal trauma, for these kids you really need to consider Lyme and test for Lyme."

He called the study helpful to clinicians because it raises awareness about the "fairly high" incidence of Lyme arthritis. "This is not a rare, reportable case. The incidence is very real."

Dr. Milewski and Dr. Ganley have reported no relevant financial relationships.

American Association of Orthopaedic Surgeons (AAOS) 2010 Annual Meeting: Abstract 141. Presented March 10, 2010.


Lyme arthritis in children. An orthopaedic perspective

RW Culp, AH Eichenfield, RS Davidson, DS Drummond, MR Christofersen and DP Goldsmith 

The cases of forty-three children with clinical and serological evidence of Lyme arthritis that was diagnosed between August 1983 and July 1985 were evaluated. The mean length of follow-up was twenty months, with a range of five to thirty months. All of the children lived in or had visited an area where the disease was known to be endemic. Arthritis was the presenting feature in more than half of the children, and half of thechildren had initially consulted an orthopaedic surgeon, none of whom made the correctdiagnosis. Only twenty patients had a history of erythema chronicum migrans, the characteristic rash that precedes the arthritis, and for onlynineteen children was there any recollection of having been bitten by a tick. Three patients had Bell palsy and one had a popliteal cyst in conjunction with the arthritis. All of the patients had oligoarticular involvement. The knee was involved in all but two patients. Recurrent attacks of synovitis were common. Effusion was the only radiographic abnormality that was observed, and it was found in thirty-two patients. The sedimentation rate was elevated in thirty of thirty-six patients.Immunofluorescent serology for Lyme disease, which is sensitive and specific, was uniformly positive. Of thirty-three patients who were treated with oral administration of penicillin or tetracycline alone, thirty-one responded, while two patients who had recurrent attacks of the diseaseresponded to parenteral administration of antibiotics. The remaining ten patients responded to combinations of orally and parenterally administered antibiotics. Longer follow-up is needed to further document the apparently low rate of relapse after antibiotic therapy in this young population.