Don't be so quick to believe it is not genetic. I have had a few yorkies with LCP and seen more thank I can count on this forum over the years. It IS thought to be genetic and any breeder who has a pup with it is advised to remove the pup from his/her breeding program. Reputable breeders DO have their breeding stock checked for LCP
Orthopedic Foundation for Animals: Legg-Calve-Perthes