Striker tested free of patellar luxation. I can decipher the OFA number for you:
RAT = Rat Terrier, PA = Patellas, 427 = Test sequence number, 18 = age in months when tested, M = male, P = practitioner (regular vet, examined the dog, as opposed to specialist), NOPI = No Permanent Identification (means that dog is not tattooed or microchipped).
No results at all on OFA for the mother? Maybe the breeder just had her vet checked, you could ask.
A vet can GENTLY check patellas on an 8 week old puppy, but at that age one needs to be very careful with those little knees. My vet doesn't even try on my Toy pups (that are 1 3/4 to 2 pounds at 8 weeks), he says there is too much risk of hurting them. He'll generally check patellas at 4-5 months when they go back in for their first rabies shots, and then again when they are nearing the time for the first breeding.
LP is not a fun thing to deal with, but it's fixable. Check your private messages, I sent you some information about the surgery.