Looking for some other info on the Cat Site and I thought I would join this conversation.
I have a healthy 3 and a half year old tripod called Trinity. We found her on the street with a badly injured (severed) hind leg and so it was either amputate or put her to sleep, and I just couldn't do the latter! She was only about six months old and very malnourished/underweight but survived it all well.
Getting her through the weeks after the operation were interesting (adapting to a new home, another cat and no leg) but we got through it. Your cat might seem a little depressed, because Trinity certainly did, in the weeks after the operation. Her wound took ages to heal and had to be restitched as it wasn't healing. After a few months, she had a go at climbing a tree, and I think to all our surprise, she could do it!
Her muscles eventually got really strong on the front of her body, and her tail eventually moved to the other side for balance and the muscles are also strong there too. She can pull herself onto anything - the bed, couch etc, but she can still jump with ease.
One major issue with tripods is weight management, you really have to make sure they don't get overweight and put too much weight on that one leg.
She is a very tough little thing now and I usually forget that she only has three legs because she gets around just like any other cat.
Good luck and please contact me if you are having any trouble.