Thanks for posting the links.
That ol' "push the leg down" trick for extension is really brutal! Here is a better way that uses gravity and is a lot more gentle on your tender knee. Start slowly with no weight on your foot (not even a shoe) for 5 minutes...less if it becomes very uncomfortable. You can do this several times a day.
3. Lie face down on a bed with the edge of the bed at about knee level or just below. Let your lower leg hang in the air. Start with a period of about 5 minutes several times a day and add another 5 minutes every 2-3 days until you reach 20 minutes a couple of times each day. Once that is comfortable, start adding weight to your ankle. Begin with 1 lb. and gradually add another pound of weight (to a maximum of 5 lb.) each week for the 20-minute sessions.
There are more exercises in this article:
Exercises for Extension