A 13-year-old running back injured his left knee while being tackled. He sustained a blow to the anterior/medial aspect of his left knee while in a flexed position. He complained of immediate pain and was unable to continue activities. He did not recall hearing or feeling a pop, but had immediate swelling of his knee. There is no history of prior knee injury. There is no significant past medical or surgical history. He takes no medications and has no known drug allergies.

Initial treatment by the coach included ice, a compression wrap, and crutches.

He was evaluated the following day by the athletic trainer and team physician.

Examination revealed a well-developed male in moderate distress because of pain. He had a moderate sized effusion with soft tissue swelling around the superior/lateral aspect of his patella and distal femur. He was not able to bear weight or fully extend his knee because of pain. PROM: (L) 20-90 degrees; (R) 0-130 degrees. The leg was warm and well perfused. The patient was tender over his quadriceps tendon, superior pole of the patella, and distal femur. He had patellar apprehension. There was no joint line tenderness. He had normal pulses and his sensation was intact. Ligament testing was not performed because of the patient’s pain. He was placed in a knee immobilizer and sent for radiographic examination.

Initial Differential Diagnosis Based on the History and Physical:

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