Surgery would undoubtedly be the best option for you. You have described yourself as an active person. The prognosis for you if you do not do surgery is that you will not be able to participate in many sports activities, and that you have a 90-95% chance of developing arthritis in the joint after 12 years, since your joint will be unstable.
Combined knee injuries are always an indication for surgery. By doing the surgery, you have a very good chance of regaining your sporting life. The chances of developing arthritis will in fact, reduce if you do the surgery, since your joint will have become stable.
"Activity, not age, should determine if surgical intervention should be considered."
This is a quote form the American Academy of ORthopaedic Surgeons. Some studies have in fact shown that older active persons do better after surgery since they are motivated and sincere about rehabilitation exercises after the surgery than younger patients.
Hence, all reports are in favour of your doing the surgery, and this is undoubtedly the best option for you.
You may consult this site of the AAOS:
http://orthoinfo.aaos.org/indepth/thr_report.cfm?Thread_ID=14&topcategory=Knee


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