HISTORY: An 18 year old volleyball player presented with acute swelling and pain of her right knee with associated nausea, vomiting, and subjective fevers. Aside from an abrasion beneath her knee sustained during practice 2 weeks prior, she denied inciting injury or trauma. She complained of knee tightness, but denied feelings of instability or mechanical symptoms. She denied history of skin or soft tissue infections. PHYSICAL EXAM: On initial examination, she was febrile to 102°F (38.9°C). She had notably increased warmth and erythema along the lateral aspect of her right knee with tenderness to palpation. She had evidence of a healed abrasion inferior to her right knee without an associated joint effusion. There did appear to be swelling localized to the lateral aspect of her knee. She had full range of motion of her right knee without any indication of ligamentous injury. Her gait was non-antalgic. DIFFERENTIAL DIAGNOSIS: 1. Septic prepatellar bursitis 2. Necrotizing infection (cellulitis, myositis, fasciitis) 3. Septic arthritis 4. Morel-Lavallée Lesion 5. Reactive arthritis (gonococcal, chlamydial) TESTS AND RESULTS: 1. Pertinent labs: White blood cell count 27,000 X 109/L, sodium 127 mEq/L, potassium 3.2 mEq/L 2. Blood cultures negative times 2 3. Lower extremity MRI: Extensive cellulitis and probable phlegmon in subcutaneous fat throughout the distal thigh and knee; myositis in the distal vastus lateralis muscle and biceps femoris 4. Gram stain from I&D right thigh: Positive strep pyogenes (group A) 5. Surgical findings consistent with necrotizing fasciitis. FINAL/WORKING DIAGNOSIS: Subacute necrotizing fasciitis TREATMENT AND OUTCOMES: 1. She was initially treated with broad spectrum antibiotics, subsequently tailored to culture and sensitivities. 2. She underwent three surgical explorations to assess underlying muscle and fascia, including I&D of necrotic tissue along iliotibial tract. 3. With both subjective and objective improvement, she was discharged from the hospital to complete one week of IV Ceftriaxone. 4. She was cleared to start her rehabilitation and progressed to walk/jog/jump for four weeks focusing on quadriceps strengthening. 5. After one week of non contact play and sport specific drills, she returned to full contact practice six weeks after hospital discharge.