Here is an interesting article I posted a while back, just one persons opinion on LP.
HIPS, KNEES, & ENVIRONMENT, by Barbara (BJ) Andrews
My belief is that improper structure and environment play a big part in the development of lp. Those dogs with improper structure, like straight stifles, will be more likely to develop lp at a early age, especially if they are jumpers. Dogs that are not as active that have proper structure may or may not develop lp until they are older, just as us humans develop bad hips and knees when we get older, especially if we are over weight.