Your title says bad knees, but your post says weak knees.
Which is it? as that can matter.
With what exactly have you been diagnosed?
“We cannot change the cards we are dealt, just how we play the hand.”
~ Randy Pausch
"There's a difference between interest and commitment. When you're interested in doing something, you do it only when circumstance permit. When you're committed to something, you accept no excuses, only results."
~ Art Turock
"We have a saying in Tibet: If a problem can be solved, there is no use worrying about it. If it can't be solved, worrying will do no good."
~ 7 Years in Tibet