I'm thinking he was beaten, imprisoned, roamed the region out in the elements often, and was even in a shipwreck at one point. All that wears and tears the body. IF it was a disability, (and we can't really say for sure for that one), we don't know which part of his body gave first. I can see arthritis. I can see rheumatism. I can see broken limbs never given modern medical treatment, years later. I can see many possibilities that his body could have been given. I am biased in thinking it was a disability, but... at least I know it's bias, not biblical.