Slim down your knees? LOL. Sorry, I found that pretty funny.
Ahem...anyways. Cardio and a little bit of pull ups, chin ups, push ups, dips, crunches, etc.
should be sufficient. Idk what you have access to so I just threw out a bunch
of exercises that most ppl are already knowledgeable about.
Oh and btw try to fix your diet. No point in losing weight if you are going to just lose muscle.
Most ppl believe their diet is good, but losing 16 lbs in 3 days is definitely not good.
So eat about 4-6 portions a day. Be sure to get in a sufficient amount of protein, carbs,
and vegetables in your body everyday. Also, drink lots and lots of water.
A full glass of water before eating should do the trick. Well, good luck.