Ditto on TSandM, on the extent.
I've had my right knee done 3 different times (1 for skiing backwards and falling in someone else's hole while doing a spin turn; 1 while whitewater kayaking, and the flooded river surging over me while getting back in my boat; and one walking off the edge of a pool while taking photos <<<< only true "klutz").
In the first one, it took three months before I could play soccer again. The second one, I did rehab, and was fully released in 10 days. The last one, released in 7 days. The key is doing the rehab, and being serious about it. If they're only removing a little cartilage, and maybe some spurs, they'll probably have you on a stationary bike inside of two days; but as pointed out, you need to let your doctor tell you. If you do PT (highly, highly recommended), they'll be able to discern lateral stability.
You can get in the water without a giant stride, you know. Simply put your gear in the water, go down the ladder, and don your gear in the water. No torque whatsover to your knee. One of the most highly recommended things in PT, to get the strength back, is swimming. It is a zero impact excercise, which works all of the main muscles. That, biking (the PTs like biking, as it's a larger range-of-motion), and the exercises they will give you with the surgical tubing will work wonders in a very short amount of time. Again, your PT will tell you not to overdo it, but with 3 of them on the same knee, I was able to dive within 2 weeks on the last two.
Good luck on your surgery and recovery.
