Daniel Gatto is a 41-year-old stockbroker. Once a top level soccer player, he now plays the game only over weekends, though he is sometimes able to get out for his club's midweek practice session. He enters your walk-in clinic on a Tuesday morning, limping slightly and reporting that he has been having increasing problems with his right knee over the past month. The knee has been intermittently painful and has seemed swollen from time to time. He has also been concerned about what he describes as "a feeling of weakness" of the knee, as though it was about to "give way"