I have a weak knee that I sprained while training for a marathon about five years ago. While it doesn't cause me any functional impairment, I have a near-consta

I have a weak knee that I sprained while training for a marathon about five years ago. While it doesn't cause me any functional impairment, I have a near-constant dull ache in my leg from the sprain and from the other muscles remaining under tension in what I assume is an effort to hold my leg together.