Working Diagnosis:
Lyme Disease/Lyme arthritis

Treatment:
Upon presentation to the clinic, the patient had an ultrasound guided knee aspiration. About 50 mL of serous fluid was aspirated. The fluid was sent for analysis as above. MRI of the knee was obtained to rule out structural disease as the patient had a history of right knee injury before the initial episode of knee swelling. Because the patient lives in an area endemic to Lyme disease, there was a high suspicion of Lyme disease. Serum Lyme ELISA was obtained and the patient was placed on doxycycline 100 mg twice daily until follow up.

Outcome:
The patient followed up one week after lab analysis and MRI were completed. Serum ELISA, serum PCR, and synovial fluid PCR were all positive for Lyme. MRI of the knee was unremarkable for structural disease. He had no recurrence of the right knee effusion at follow up. He was cleared to begin gradual return to activity as tolerated and gradually returned to his prior level of activity. The patient was continued on doxycycline for a total of four weeks and continues to follow with an infectious diseases specialist. To date, he has had no recurrence in his symptoms.

Author's Comments:
Lyme infection is not uncommon in the mid-Atlantic area of the United States, including eastern West Virginia.

Editor's Comments:
Lyme arthritis can manifest with either intermittent or persistent symptoms. The most common joint affected is the knee. Monoarthritis is the most common finding but asymmetric oligoarthritis is also possible, which typically also includes the knee. Other than the knee, the most common joints affected are the shoulder, ankle, elbow, wrist and TMJ. Bursitis and tendonitis around the affected joints is possible. When more than one joint is affected, it typically does not involve more than five joints. Episodes of joint effusions occur abruptly and can last weeks to months. Effusions tend to be very impressive especially in the knee and often recur even after aspiration. Bakers cysts are a known manifestation in the knee. The arthritis that accompanies Lyme disease is not especially painful. Typically once the arthritis is resolved there is little if any residual joint dysfunction, but in rare cases there can be persistent arthritis that leads to cartilage erosion and permanent joint damage. Systemic symptoms are rare in Lyme arthritis but in those with extra-articular symptoms, fatigue is very common.

References:
Hu, Linden. Clinical manifestations of Lyme disease in adults. Up to Date August 17, 2016

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