DJD isn't really a "disease" in the sense of the word that most associate disease with. It's your body breaking down as you age. It happens to everyone, just at varying rates. Some people have degeneration early, some later, different joints, etc...
Very common for knees to have DJD. The cartilage in your knee will can soften, break down, deteriorate. It can be made worse by other factors, such as injury, bone spurs, etc... Yes, it's treatable through different methods. Injections can be done. Yes, they hurt when they're done, but they can give you a significant amount of relief for quite a while. One thing I would very much suggest is strengthening the muscles around the leg joints. The stronger you make those muscles, the more support your joint will have. Unquestionably check with a doctor before doing any exercise, so you know what you can and cannot do. Anti-inflammatory drugs such as Advil can help (I can't take Advil). Surgery can depend on your age, condition, how far along the degeneration is. The very, very end of DJD is joint replacement if it ever advances super far to where it's bone on bone. But don't worry about that now, you may never need it.
I've had knee (and other joint) issues since I was 12 or 13. I'm 45 now. I had surgery on both of them when I was about 25 years old to try to help. It had limited success. Honestly, for the longest time I tried to be "conservative" with my knees in that I didn't run, etc... Probably did that from right after surgery until I was about 35. Then I started having issues again, and my doctor suggested building muscle around my legs. That's what got me started into weightlifting and bodybuilding. I'm not suggesting you need to go into all out bodybuilding, but I will say that strengthening my leg muscles has been the best thing I could have done. My knees still aren't perfect, but the past 10 years have been far better than the previous 15. Much less pain, I'm able to do so much more...I can run 5Ks, I even trained for a half marathon several years back. I can run, jump, etc... One of them is starting to become a problem again, but I'm no spring chicken, so it is what it is.
One cool thing I can do is "pop" my knees. Just like people crack their knuckles, I can do the same thing with my knees. It's LOUD, and makes for a great party trick.
Best of luck and don't let it get you down. My hips are also degenerating, I already had surgery on one of them 3 years ago. My attitude is that until they (hips, knees, whatever) completely give out, I'm going to use them and enjoy life to the fullest. I'd rather get 10 years of playing with my kids, exercising, and just being active before needing to replace them than 20 years of sitting on the couch.
