"He had not cared for his feet." Mephibosheth's feet were crippled. This phrase means that he had not taken proper care of his feet.
# Why did you not go with me, Mephibosheth?
David is asking Mephibosheth why he did not go with David when David and all the people who followed him left Jerusalem. AT: "Why did you not go with me when I left Jerusalem, Mephibosheth?" (See: [[rc://en/ta/man/translate/figs-explicit]])