What can i do at the gym to that wont hurt my knee??

Hi... My name is Ashley and I am a 26 year old Mommy :-)
I have been stuck at my weight for months now!!! 4 years ago i was actually underweight, i weighed 95 pounds before i became pregnant with my daughter, had a terrible pregnancy was on bed rest and the day i went into labor i weighed 205 lbs!!!!!

Through dieting I went down to 159 and was feeling great and motivated to reach my goal of 130, Then i was diagnosed with endometrosis and went on a Lupron shot... (it is a 6 month shot that puts your body through a temporary menapusal state) Major side effect is weight gain... I went back up to 180 in three months...

The shot is no longer in my system but I cannot seem to drop the weight! for the past three months i have been watching what i eat and havent lost a pound... then two weeks ago i came back on to MFP and joined the gym...

I have been going to the gym everyday except sundays and sometimes twice a week doing mostly cardio... some leg and butt machines to tone.. (legs and butt are what i like most about my body)

Yesterday my knee gave out and i went to the ER and found out i tore my Meniscus in my knee...

Doctor said No gym for now and is talking about surgery...

Main question!!? HOW DO I LOOSE THIS WEIGHT!!!! I am 5'7" and have a very small frame... My stomach is huge... If i am not sucking it in i look very pregnant... also my love handles are ridiculous!!! i am so oddly proportioned!
The weight gain has caused Back pain, knee issues and now some heart issues?


Help
Thanks in advance!!!
Also add me I would love the support and motivation!!