Help Tucker Walk!

Two years ago I rescued the now love of my life, my dog and best friend, Tucker.   I was a full-time sophmore in college when a co-worker of mine approached me saying she was unable to care for her newly rescued and adopted Rottie-Shepherd mix puppy of about 8 months old.  It was love at first sight for my whole family the minute he came into our lives.     He loves to play outside more than anything in the world, running around, chasing after squirrels, playing fetch and all other things young doggies love to do.  Unfortunately it was due to his love of playing that he injured himself and tore his ligaments in his right knee.  We learned that because of his mix of breeds, hia very skinny shepherd legs are unable to support his muscular, Rottweiler body even at a healthy weight.  It has been recommended to us that he needs to be almost underweight in order to be able to support himself properly.     It breaks my heart that my three year old baby is unable to come outside and play fetch with me and has to be kept on a leash at all times, even just to go outside in the back yard.  I'm absolutely gutted when he stares at me with the hugest brown eyes, filled with sadness that he's in so much pain and I'm unable to help him.  I just want my boy to be able to be able to play again, I want him to be able to do what he loves everyday for as long as he lives.  I want his happiness back, and I need help.   I brought Tucker home and my family welcomed him with warm, loving arms and I just can't bring myself to ask them to help me with this procedure for him.  My parents and family have been nothing but wonderful to us, helping me take care of him and loving him, but asking them for this would put an absurd strain on their own financial lives, and I could never do that to my family, not when they've already helped us this much.  I've been trying to do my best on my own with him and his vet bills; I work full-time while attending school full-time and do my best as a doggie-mommie to juggle everything to the best of my abilities.     Any help would be beyond appreciated, I just want to see my baby be able to run around again.  Help us to help Tucker walk, help us to give Tucker back his happiness!