Yes, you can live a long and successful life with a bad knee or shoulder. But, once your brain is injured and your mind stops functioning as you need it to function, a healthy body is of little value.

I have a friend who has been in a wheel chair since 11 years old (30 years). Her bright and active mind allows her to do anything she wants if she can just roll up to the location. I sometimes look at her and think that it would be easier to live in a wheel chair than to have to live with cognitive and memory dysfunctions.