After it happens once, it is likely to happen again. Poquita lived with it all her life. Don't let anybody play with him in a way that requires him to jump, ie: frisbie or catching treats, etc. I learned via web how to put her knee back in place (verified w/ ortho vet) and we went on like that for many years. At age 7, we had her evaluated for surgery and the ortho specialist said Poquita's tendons had adapted so well from walking the park every day, that he wouldn't risk surgery. She was a tiny dog, 5-6 lbs. She did develop arthritis as had been predicted but only was really incompacitated the last few months of her 15½ yr life. Rosie, however, had an ACL tear a few years ago and did need surgery. $3K but she did well. I've actually heard of luxated patellas in big dogs, too, so it happens.