Disclosures: Sophia Yae, DO: No financial relationships or conflicts of interest

Case Description: A 17 year old male basketball player presented with acute onset right knee pain and swelling for one week. He denied any trauma or inciting event during recent basketball games. Pain was described as aching and non-radiating. It was worse with activity and improved with rest. He denied any recent sexual activity. Physical exam revealed an obvious right knee effusion without warmth or erythema. He had mild tenderness over the medial patellar facet. Ligamentous and meniscal testing were negative. Aspiration was performed, yielding 93cc of straw colored synovial fluid, and the patient had complete resolution of his symptoms.

Setting: Sports medicine clinic

Patient: Adolescent male basketball player Assessment/

Results: An MRI showed a moderate effusion but was otherwise normal. Synovial fluid analysis was negative for organisms and crystals, but significant for 20% eosinophils. CBC showed no eosinophilia, and serum electrolytes, ESR, CRP, and liver enzymes were all normal. Three weeks later, the patient’s swelling reaccumulated. Additional bacterial and fungal cultures were performed on the synovial fluid, all of which were negative. The patient required a total of 3 joint aspirations for pain relief within a 6 week period. Rheumatology was eventually consulted and advised treatment with NSAIDs.

Discussion: A high concentration of eosinophils in synovial fluid is an uncommon finding that is usually associated with rheumatoid arthritis, parasitic disease, hypereosinophilic syndrome, hemarthrosis, or arthrography. Studies show that the presence of eosinophils does not usually correlate with peripheral eosinophilia. Eosinophilic synovitis is considered idiopathic when all other clinical and laboratory evaluation is reassuring and a known rheumatic or systemic pathology is excluded. Treatment includes NSAIDs, compression garments, or intra-articular corticosteroids if needed.

Conclusion: Idiopathic eosinophilic synovitis is a rare cause of knee pain and swelling. Musculoskeletal providers should be aware of the diagnosis and treatment options, especially when treating athletes, as an effusion typically indicates more severe pathology.

Level of Evidence: Level IV

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/idiopathic-eosinophilic-synovitis-in-an-adolescent-basketball-player-a-case-report/