Need Advice

I'm a 25 year old army officer. I've played contact sports (football and rugby) for most of my life and I am currently in an airborne unit. I had knee surgery to repair torn medial meniscus (result of a football injury) about 11 years ago. Since that time I had no problems with my knee despite playing rugby and soldiering until the spring of 2002. I slightly injured the same knee during a rugby practice. It was swollen for a couple of months but the pain was not very bad. Since the injury I have lost a couple of degrees of range of motion in the knee. It was a busy time for my unit and we were getting ready to deploy to Afghanistan. I have since seen a doctor and he told me that I have osteoarthritis and require an osteotomy. I put off the surgery to deploy with my unit to Afghanistan. I exercise quite often and my job is very demanding on my body. I have slight discomfort on days where I have to march or patrol (on foot) particularly far. For the most part my complaints center around the loss of range of motion. What are the chances of me not having to have an osteotomy? The only bone I’ve ever broken is my nose so I’m not keen and the procedure. I’m otherwise very healthy and fit. Are there other options? Will I still be able to do my job after the surgery? I don’t understand how after I can go from having no problems to suffering a minor injury and than developing osteoarthritis. Any advice that is out there would be greatly appreciated. On my return home I do plan on getting a second opinion but that is still several months away.