Helping Monk get back on his feet

Hi, my name is Conor and I have been the happy and proud dog dad to my amazing best friend, Monk, for 2+ years and he has been in my family almost 6 now! He's been my camping and hiking buddy for a majority of my time living in Montana and I couldn't have asked for a better friend. Sadly, a lot of that has come to an end as a few months ago he had an injury to his cruciate ligament and it has really begun to impact he quality of life even just walking around the house these days. Im looking into several different options right now and seemingly only surgery is a viable option now.. I am worried that as time goes on his other leg might begin to fail under the strain of using it more than his injured one. He is only 9 year old right now and still has many years left ahead of him and I want to make it as comfortable as I can for him and if it means getting the surgery, ill do what ever it takes to help out my best friend!