My vet said my kitten might have soft bone disease. is he going to die?

our kitten was x-rayed and found a broken hip bone and knee cap from no apparent injury. he is indoors only. ever since we got him, he has wobbled on his feet and then his walking got progressively worse until he would "roll" his hips to get around and drag his body by his little arms. other than his walking, he is vibrant and loves to play, eat and enjoy life. i can't imagine putting him down because of this. his walking got a bit better on anti-inflammatory drugs and he was able to get around until he broke his two bones for no apparent reason. any opinions on what the heck to do?