you know, a couple of years ago my dog's back legs gave out too. He couldnt even walk to go outside or go eat his food. He would just lay on a blanket we put out for him and every so often my mom would carry him outside, put him on the ground, and lift his back leg so he could go to the bathroom. We took him to the vet and they said he had a serious back problem and wouldnt walk again unless he went into surgery which was $500! My family and I love our dog put we were just not going to put out that kind of money for him..... it all worked out for the best though because about two weeks later he started walking....miraculously.... since we were told he would never walk again
Ever since then he has been able to do everything.... he stands on his back two legs to ask for a "treat"

goes up and down the stairs probably faster than me

and he used even jump on the sofa when we werent home
Even though my dog is old, he is going strong because he doesnt do anything but sleep and eat all day long! He even gets hyper when its cold out!