I'd have to guess that it's simply bad luck

Some of the articles were saying that he suffered that injury after taking a direct hit on his hip. While building up muscle around that area can cushion things, that can only go so far, especially if you get hit in just the right place. If anything, that kind of a situation reminds me of the 1991 NFL season, when Randall Cunningham busted up his knee when Bryce Paup nailed him, and the stress was localized to just the "right" area.

Loren Landow is one of the best in the business, with a very well proven track record.