Ways to lose weight with an injured knee?

I am trying to lose weight that I gained due to the injury I sustained to my knee and ankle. I gained about 20 lbs over an 8 month period. I was over weight before but not by much but this weight gain pushed my ons to the point where I do not want to look at myself in the mirror. I am in physio therapy however due to travel reasons and the cost per one hour I go every 2 weeks and have exercises I do at home. I also just bought some easy to do work out DVDs that don't allow me to strain my knee. I also eat fairly healthy however I do sometimes slip up and eat chips or have pop. So please give some great and easy to follow tips to help lose weight safely, easily, please ensure it is also fun and not boring.As I will be more likely to slip up! Thankyou I appreciate it soooo much!!!