Knees let Nadal down again

Question

It looks like Rafael Nadal’s knees have failed him again as he was forced to retire from his 2010 Australian Open quarter-final against Andy Roddick. The problem – knee tendonitis – was first diagnosed in late 2008, and by mid-2009 Nadal was forced onto the sidelines again. Now, just when it looked like Nadal was on the mend and rebuilding his game, it looks like the injury has flared again.