I had surgery last month on my knee, and because of that I am now going through physical therapy. I want to lose weight and gain definition, but it seems kind of hard to do without the use of my knee. Im not sure when Ill be able to run or swim again. I really want to have something to show for my work before the last week of August. I have an average body, my friends tell me I'm fine, but I dont agree. I just need to get moving again. Any exercise tips?

Swiming is easy on the knee and a great cardio/workout.

You can do lots of upper body while being careful not to do anything to your knee.

Keep your diet clean, workout the upperbody and swim if you can.

Punches and speed bag can get your heart rate up without putting stress on the knee.

Swimming, I was swimming after only a couple of weeks after my knee surgery last year (No breststroke though).

I cant swim. I really dont want to explain that quirk. Thanks for the tips though.

Well there are 'bikes' out there for your upper body that you can do for cardio but their hard to find.

Another way to get 'cardio' in without running/swimming/biking/etc is weight training with no rest... its hard but can keep your heart rate up also.

You can do something Like

Set A
Perform 5 sets
Benchpress 15reps Move to next machine immediately
Pullups (or pull down machine) x10 (use assistance if doing Pullups)
30 second rest, move back to Benchpress

Finish 5 sets of Set A move to Set B
5 sets
Shoulder Press x10
Tbar or other chest supported Row x10
rest 30 Seconds & move back to Shoulder press.

etc.

Build a program that does push/pull switching and keep moving... you'll be huffin & puffin. Use a weight also that leaves 3-4 reps in the bank.