It's the same for elbow screenings, too--the breeder (or owner) can specify that if the results show dysplasia, they aren't to be included in the public database...which makes the database a much less than perfect tool. Ethical breeders often have all the results published, both good and bad. How do you tell, though, in the case of all positive results, if a breeder's lines are just that good, or if bad results are being suppressed? Very hard to tell...so results published in the OFA database by a breeder is a plus, but shouldn't be assumed to be the whole story. An ethical breeder will be willing to discuss incidence of dysplasia or disease known in their breeds/lines when asked, however.
Nonbreeding owners can also have results posted in the public database, and since they often have less at stake than the breeder would, they're often more honest about the results. We've made sure to have all the screening results for our dogs published, both good and bad.
"We are--each of us--dying; it's how we live in the meantime that makes the difference."
"It's not what you gather, but what you scatter that tells what kind of life you have lived!"
"Be kinder than necessary, for everyone you meet is fighting some kind of battle."