Our pup had it done a few years ago, while she was recovering, the other one went out. Between the two procedures, she was drugged and in a pen for over 6 months. It took about another 6 months for her to fully recover, not sure if it was from the procedure or all of the meds she was taking. She was a whole new dog though, tons of energy and always wanting to play. However, 3 or 4 years later now, she is getting some arthritis in the first knee they did. We have been giving her joint supplements, which seem to help. It doesn't appear to bother her once she is moving, but when she goes to stand after laying down for a while, it looks a bit painful.
