Please Help Doc !!

Putting Doc down is not an option!! Doc is in need of a surgery on his back leg. He dislocated his knee cap and tore his cruciate. He is unable to use his back leg.  I had his other leg done 3 months ago and he as now has the same injury on his good leg and I can not afford this amount so quick again.  He can barely walk because of the injured leg he can not use and his recovering leg is not strong enough yet to support his body weight.  He is absolutly a great dog and deserves to have his leg fixed and have a good quality of life.   Doc is 3 years old. I adopted him when he was 12 weeks old from a rescue that I now am a part of. He was found left in a dumpster. Doc is the reason I became a part of Animal rescue. He is a loved family memeber. Not only a family memeber he is great at helping me socialze my fosters. I would not normally ask for help but I have been left with no choice since I just paid for the 1st surgey. Any hep is greatly appreciated.