Nothing is going to work unless you have your diet in check, in addition up your cardio to 5 days a week/ 30 first thing in the AM. I can promise you that you will be disappointed if you think winny or any AAS is going to be some kind of miracle weight loss formula. Get your diet together post in here and let us view, maybe add suggestions, etc.
We know nothing about you, except that you have been offered winny, you have a bad knee, and you want to lose weight..
How about telling us..
-What you eat every week on a daily bases/How many meals a day.
-How many calories/fat/carbs
-How long have you been trying to lose weight (I noticed you said you are doing decent amount of cardio, how much is that? And I would think that you would know that a decent amount of anything doesnt cut it.)
-Give us your stats, age/weight/bf?
-How long have you been going to the gym
But if you really must take something:Here is the best supplement for weight loss...................Wait for it............................... Take 30 minutes of moderate intensity cardio 30 minutes a day 5 to 7 days a week. I promise you the weight will fly off- Diet,cardio,diet,cardio,diet,cardio
Thats all I have to say......... Now start running