Corey Yuen leg injury?

[Tonic]

I just got the EDKO DVD release of Dead or Alive the movie, naturally I was bored through most of the film.

However when looking through some of the special features, I spotted this:

<a href="http://img411.imageshack.us/my.php?image=corey1di5.jpg" target="_blank">One</a>

<a href="http://img137.imageshack.us/my.php?image=corey2hs1.jpg" target="_blank">Two</a>

Looks like a pretty nasty leg injury Corey has - I had not heard anything about it before, is this recent? or is this the reason he didn't do any action roles after the 70s pretty much?