Do I think his injury prone status is a bit overblown? Yes. People forget that in 2004 the eagles sat healthy starters for example. What contributes to this is the fact that he routinely manages a Probable or Questionable status week after week, even when come game day he looks healthy and puts up great numbers.
However, one would be foolish not to consider him more injury prone than most of the other top RBs. He's had a couple serious injuries (none to those knees thankfully), and his size doesn't help him take hits too well. Westbrook is not for the faint of heart. If you constantly worry about a guy because he's missing practice, or just won't risk starting a guy who might be "Questionable" nearl half the season, you're going to hate taking Westbrook. However, the rewards certainly balance out the risk. Not nearly as much this year, but with so many questions, here's a guy whose points per game has been top 12 for the past 3 years, at some point you have to decide between unprovens with healthy track records, or big time performers with other known issues.