text: what could it be? my relative has been disabled for just over a yr now, but no doctors have properly diagnosed her. she has cronic lower back pain which means her legs give in at any time and therefore she is unable to go out. she is constantly in pain and cannot sit down she has to lie on one side. before she was like this she had kidney stones could there be a link? it's most likely a spine problem of some sort.  the spine controls the nerves and the nerves in turn control the muscles. if the legs are weak and he/she is having back pain, most liekly their is something gong on with the spine. take 'em to a good orthopedist.