a 69-year-old man with a 2-week history of pain and swelling in his left knee.

Steve Saunders, PA-C
The author practices in an orthopedic office in Norwalk, Conn. He has
indicated no relationships to disclose relating to the content of this
article. Erich Fogg is Assistant Professor in and Program Director of
the Physician Assistant Program at the College of Health Professions,
University of New England, Portland, Me.


CASE
The patient is a 69-year-old man who presented to our office with a
2-week history of pain and swelling in his left knee. These had
worsened during the past week, making it difficult to walk, climb
stairs, and flex the knee. The patient works on a golf course in
southwestern Connecticut and reports no history of trauma. He denies
any fever, chills, sweats, or tick bites. He had been taking an
anti-inflammatory prescribed by his primary care physician for
arthritis, but it was not relieving his symptoms. He has a history of
hypertension and hypercholesterolemia and takes amlodipine (Norvasc),
ezetimibe (Zetia), and rosuvastatin (Crestor).

On examination, the patient exhibited an antalgic stiff gait with some
difficulty getting into or out of a chair, and a large, tense effusion
was noted in the left knee. A radiograph of the knee is shown in Figure
1. The patient also had limited range of motion and diffuse tenderness.
He was afebrile with no signs of systemic illness, and the rest of the
physical examination findings were normal.

The patient's knee was aspirated, and 60 cc of cloudy synovial fluid
was removed. The fluid sample was sent to the laboratory for cell
count, Gram's stain and culture, crystal analysis, and Lyme
polymerase chain reaction (PCR). Blood was drawn for a CBC, Lyme
serology, and ESR. The patient was sent home with instructions to rest,
ice, and elevate his knee and to continue taking the prescribed
anti-inflammatory medication.

Laboratory results included the following: The CBC with differential
was normal, and the ESR was 44 mm/h. Lyme disease, Western blot, and
PCR test results were pending. The Gram's stain was negative for
bacteria but showed many neutrophils. Bacterial cultures and synovial
fluid analysis were pending.

WHAT IS YOUR DIAGNOSIS?
Septic arthritis
Gouty arthritis
Lyme arthritis
Osteoarthritis
DISCUSSION
That evening, the patient presented to the emergency department with
increased swelling, warmth, erythema, and a fever of 101¼F (38.3¼C).
His knee was again aspirated, and the synovial WBC count was 293,000
cells/mm3, predominantly neutrophils. Septic arthritis was diagnosed,
and the patient underwent arthroscopic irrigation. Arthroscopy revealed
copious yellow, purulent fluid; significant synovitis; and some mild
osteoarthritic changes. The Gram's stain remained negative, and
bacterial cultures were negative, including of the initial office
aspiration. An infectious disease specialist was consulted, and the
patient was started on IV vancomycin and ceftriaxone. During this time,
his hematologic WBC count never rose higher than 10,000 cells/mm3. The
ESR rose to 100 mm/h. The results of tests-including screen, Western
blot, and PCR-for Lyme disease were grossly positive. Bacterial
cultures remained negative throughout the hospital stay. The diagnosis
was revised to Lyme arthritis, and IV ceftriaxone was administered
through a percutaneously inserted central catheter for approximately 1
month under the care of an infectious disease specialist. In a
follow-up visit to our office 2 months after arthroscopic surgery, the
patient had some mild arthritic complaints but was otherwise back to
baseline.

Days to months after the initial infection, Lyme disease can cause a
monoarthritis commonly involving the knee. A rash may or may not be
present. In patients with Lyme disease, WBCs in the synovial fluid are
typically 10,000 to 25,000 cells/mm3 and predominantly neutrophils.1 A
WBC count as high as 300,000 cells/mm3 is highly suggestive of septic
arthritis.1,2 A strong suspicion of septic arthritis, which is
destructive to articular cartilage and joint structures, mandates
aggressive treatment as soon as possible. Lyme disease needs to be
recognized and treated to prevent the development of chronic
inflammatory arthritis or the involvement of the cardiovascular and
neurologic systems. This case demonstrates that as Lyme disease becomes
more prevalent, its presentation is becoming more varied.3


--------------------------------------------------------------------------------


REFERENCES

1. Scher DM, Wise B. Infection. In: Koval KJ, ed. Orthopaedic
Knowledge Update 7. Rosemont, Ill: the American Academy of Orthopaedic
Surgeons; 2002:183-191.

2. Mandell BF. Septic arthritis. ACP Medicine 2004. Available at:
http://www.medscape.com/viewarticle/482277. Accessed August 7, 2006.

3. Centers for Disease Control and Prevention (CDC). Lyme
Disease-United States, 2000. MMWR Morb Mortal Wkly Rep.
2002;51(2):29-31.

.

Quantcast