Peter, sorry your progress is so slow. Are you able to ride at all?
I hope your doctor didn't just tell you that you have a cartilage tear, and sent you home. There are a few things you can do that will keep you more comfortable, and might even prevent you from needing surgery.

-Get a brace! If your knee is giving out 40 times daily, you could further damage the cartilage or damage a ligament.
-Take an anti-inflammatory like ibuprofen regularly. Not only will it help the pain, but it will minimize damage to the knee from the body's inflammatory response.
-Cortisone injections might help.
-Ice your knee for 15 minutes every hour if you have swelling/pain, or if you re-injure it.
-There are exercises that can strengthen the knee joint. Do them religiously (or Paganly, whichever you prefer).

I'm really curious to hear what CVOGirl thinks about her reverse gear that she installed. CVOGirl, are you out there?
Get better!
Dan