LOL
My sister has spinal muscular atrophy. Pretty much, a less aggressive form of spinal muscular distrophy (you know, the disability that has the Bow Tie Day charity attached to it). My parents had no idea what was wrong with her, and would constantly worry that she had learning difficulties, as she didn't crawl until she was like, 4 or something. Even then, her arms would constantly give way and she would fall on her face. My parents were the subject of questioning for a while, due to her injuries. The doctors thought they were physically abusing her. They finally found out what was wrong with her, and all the questioning stopped.
Basically, with spinal muscular atrophy, you can walk for a while, with the aid of leg calipers and walking frames, but because the muscles continue to decrease throughout growth, that soon stopped, and she was confined to a wheelchair. Her legs gradually lost all control, and her arms are slowly getting that way too. She only has about 38% lung capacity, so whenever a common cold is going around, it truly is a matter of life and death that she's confined to a healthy environment. The decrease in muscle capability has pretty well stopped, and she should be able to continue to do things as well as she can now, for a while yet.