Case 17-1990: A 16-Year-Old Boy with Painful Swelling of the Left Knee Joint and Calf

Presentation of Case A 16-year-old boy was admitted to the hospital because of painful swelling of the left leg. He was well until two weeks earlier, when a sore throat developed. One week before admission he stayed out of school for one day because of a low-grade fever, with headache, malaise, and a productive cough. Three days before entry he experienced "cramping" of the left hamstrings and was unable to extend his knee for about five minutes. On the following day he noticed pain and swelling in the left calf, although he was able to play tennis; both symptoms worsened . . .