He'll be right as rain in no time if that's the case Diego! I suffer from the same problem, although it took quite a while to diagnose. Every time I played football or ran for more than 20 minutes or so my right knee would swell up and i'd be hobbling for a week. I eventually had casts of my feet done (on the good old NHS) and then got some jazzy rubber insoles in my trainers and now, hey presto, I can run like the wind (cough cough).......