A Spooky Cause Of Knee Pain

HISTORY: 46 y.o male who presented with acute left knee pain, which began while chasing his daughter on Halloween and was further exacerbated by dancing the following evening. Patient reported a fever that began the night prior to his evaluation. Notably, the patient denies any history of prior knee injury, surgeries, or infections. Physical: A musculoskeletal examination of the soft tissue and bony structures was unable to be performed due to the patient’s symptoms. The patient presented to the clinic with an abnormal gait and could not perform knee range of motion. Swelling, effusion, erythema, and warmth to touch were present at the time of his evaluation. The patient was afebrile, normotensive and in no acute distress. DIFFERENTIAL: gout flare, septic arthritis, cellulitis, synovitis, insufficiency fracture, inflammatory arthropathy FINAL DIAGNOSIS: Pigmented villonodular synovitis TESTS: Synovial culture (RBC 7000, WBC 14,938, negative cultures, crystals), blood culture (negative), CBC (WBC 12.1, neutrophils 78.1), inflammatory markers (CRP 21.4, ESR 67) Xray: 1x1.2 cm subchondral lucency on medial patellar facet, large knee effusion MRI: 3x2.7x2.8 cm intermediate mixed signal intensity protruding into the MPFL with associated pressure erosion of medial patella. Reactive marrow edema in the patellar as well as muscle edema in distal quadriceps. TREATMENT: After initial evaluation, the patient was scheduled with radiology for an ultrasound guided joint aspiration. Due to initial purulent drainage the synovial fluid was sent for analysis. He was immediately sent to the ED and had blood work, blood cultures and IV antibiotics (Ceftriaxone and Vancomycin). Ultimately, he was discharged after the cultures came back negative and had completed IV antibiotics. He followed up with primary care sports medicine where a MRI was ordered. After completion of MRI, the patient continues to ambulate with crutches and has been scheduled for prompt follow up with Orthopedic Oncology.