DentonDoc wrote on Sep 20^th, 2011 at 3:40am:

According to my wife (certified yoga instructor), something like the lunge (a.k.a Anjaneyasana or "crescent moon") pose would be good to strengthen your knee muscles.  However, alignment is critical.  If you are misaligned, it could do more harm than good.  She recommends going to a competent yoga instructor, explain your injury, and have the instructor check your alignment. dd

Your wife is a smart women ;)
Before you start any home DVD exercise program that is new to you, you would be wise to take a few classes from a certified instructor.
If your doing as part of a re-hab program it's even more important.
Even the best DVDs sometimes don't allow you to see how your alignment should look from every angle.
Sometimes the difference between doing it right and safely comes down to the little things.
Lot's of people end up hurting themselves doing various workout DVDs becasue they forget that for the most part there for people that may be out of shape but don't have physical problems that need to be taken in to consideration.
You can modify almost any exercise to fit your fitness/ physical limitations. The trick is to make sure your not doing more harm than good.