Practically all small dogs are known to have LP (google it for more info). Bailey was checked for LP on her very first visit - and every visit since. My Bailey is a level 1 - meaning her knee caps slip out when pushed out and they easily slip back in. Last year - when Bailey was about 8 mos old, she limped on her hind leg a few times. The vet confirmed level 1 again and said if she continiued to limp that I should consider surgery.
Oddly, Bailey has never limped again - so we never had the surgery.
After all this - my point is that if your vet has never checked your baby for LP - and if he/she has never even discussed it with you - then mabye its time to consider a new vet??
And my personal opinion is - do not rush into surgery. My sister's terrier mix was diagnosed with LP as a puppy and her vet said the dog would probably outgrow it - and it did.
Good luck!!!