PMC8047495_01
Right knee on presentation demonstrating diffuse swelling compared to the left.
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On presentation to the ED her temperature was 37.4  C (99.3  F) and physical examination revealed marked swelling of the right knee without erythema or warmth (Fig. 1).
Joint aspirate demonstrating turbid yellow synovial fluid.
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Orthopedic surgeons evaluated the patient two days later in their clinic and performed an arthrocentesis of the right knee with 15 mL of turbid yellow synovial fluid removed (Fig. 2).
Right Knee MRI demonstrating 5.9 x 2.6 cm rim-enhancing fluid collection in the sagittal plane (A) and axial plane (B) indicated by solid white arrows.
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MRI was obtained which revealed a large 5.9 x 2.6 cm rim-enhancing fluid collection within the vastus intermedius, consistent with abscess (Fig. 3).