It is a long time since I have read an article on this subject. Just noticed this on the VBC website.
Mephibosheth disabled through no fault of his own.
2 Samuel 4:4
And Jonathan, Saul's son, had a son that was lame of his feet. He was five years old when the tidings came of Saul and Jonathan out of Jezreel, and his nurse took him up, and fled: and it came to pass, as she made haste to flee, that he fell, and became lame. And his name was Mephibosheth.