MY younger dog, AST, age 1.5 years, just had a Cranial Cruciate Ligament tearing and we had to do a surgery (TTA). The vet says this is pure genetics, since she is so young. Long recovery ahead of us, but she is walking fine after just a week (ut we have to limit her severely for 3 months at least).
The breeder denies heredity and blames trauma, so we are not getting a partial refund. The first orto vet diagnosed her with a misaligned disc in her spine and the second one (the best one in the country right now), saw right away that her limping is due to the ligament. Her spine is fine, but my wife was scared shitless for a month, because she is a vet by education and knew what spine problems would lead to.
So now, we're stuck with two dogs that cannot play with each other for almost a year and there is a 50% chance that the same surgery will have to be done on the other leg in 1-2 years. For anyone keeping count, our older dog had a series of 3 surgeries in three weeks on her intestines and almost died 6 months ago, but is now fully recovered. I'd say she is a bit less energetic for her age, but other than that she's good and we're super thankful for that.