Could this still be a problem?

Hello people, I am a male of 38 years that was diagnosed at the age of 15 with OCD in my left knee. I only wore a cast for 6 months and then I was told I was fine. In those days I wasn't the most active person, mind you a did a fair amount of bicycling and skateboarding. At the age of 18 I joined the army and then I, of course, was running usually five days a week. Things went fine for a year or two then I would start getting bad pains in my knee. Then about 3 years into the military it got very bad. My knee would swell, not very much usually but there would be swelling. Then it just started to give out while on runs. This was pretty painful to say the least as falling on your face is no fun but then when 5 or 6 people run up your back it really loses its charm. By this point I had been to army doctors 4 or 5 times and they could find nothing. Then I finally said they must look harder because some days I couldn't walk and falling on my face was getting old. They then sent me to have an MRI type examination (not an O-scope). Some about shooting dyes into my knee and using a type of x-ray (sorry but I am not a doctor). This once again revealed nothing. At this point I think I was 22 or 23. I didn't do much running for the next year or so and would notice pain after long walks or long periods of standing. I have since leaving the army became much more active and very much so here recently. I cardio train 5 times a week (spinning, stairmaster, or rowing machine) and play golf. I generally still get some serious pain 3-4 times a week. Recently after a snowboarding trip for 10 days I came home and had to go to the emergency room to have my left looked at because it was swollen, painful and made a grinding sound everytime I bent it. The doctor basically informed me that I was old and thats the way it is. So after all that is said. I guess I am still wondering if thats true. Is that the way it is? Or could there be something missed that some other procedure would pick up, like an O-scope? I am tired of the pain and it still gives out once in a while. Thanks for any help. -Jeff