I just had a request for information on knee injuries. Here are the posts I've written about that.

http://balletshoesandpointeshoes.blogspot.com/2009/07/how-to-understand-overpronation-and.html

http://balletshoesandpointeshoes.blogspot.com/2008/12/how-to-prevent-knee-injuries-in-ballet.html

http://balletshoesandpointeshoes.blogspot.com/2008/08/highly-effective-tips-for-understanding.html

http://balletshoesandpointeshoes.blogspot.com/2008/03/ballet-turnout-prevents-knee-injuries.html

Posts about turnout refer to preventing knee injuries as well - listed down on the left.