well sorry for your loss
but LP is a long time disease in many dog breeds, labs included
when BUYING a pup, is always a good idea to talk to the breeder about history on there lines, and see if its been in there lines
most ALL good breeders will be up to par on things and know what they have or don't
its a HUGE reason to buy dogs from REAL dedicated breeder that have the breeds best interest in hand and NOT just making money!
if you get on any LAB Forum, you will find many that have sadly had this happen to there dogs too, so it is sort of common in Labs!