Hi wrg1405
This is a normal later sequel to the injuries and subsequent surgery you had - and 20 years ago the surgery was not as good as now. You are too young for joint replacements and anyway from what you describe your symptoms would be too mild to even get a look in.
Personally I don't think a knee brace would do a lot for your knees - some patients swear by them but that might be more a placebo effect. A brace aims to either a) reduce instability or b) control the amount of normal excursion your knee moves through The former is probably unrealistic - an external knee brace is too puny to control such forces; the later is not what you need and in the long term would do more harm than good.
However there is a lot of negativity about osteo-arthritis which is a pity. In fact OA is basically a remodelling disease rather than a primarily a degenerative disease. It is probably the abnormal forces exerted on the joints over a very extended period of time that leads to abnormal remodelling of the joints and on to a cascade of joint changes that are causing the problems you are having. A course of active physiotherapy to rehabilitate the knee can improve the protection to the joint that the muscles around the knee should provide and exert more beneficial remodelling forces on the knee than your knees currently receive. Such beneficial remodelling actually reverses the OA process to some extent, provided the disease isn't too advanced. Even in advanced cases there can be some benefit. Such a course of physiotherapy should include a controlled programme of progressive resistance training (weights), exercises to improve the function of the muscles that stabilise the knee and graded increase in demanding activities on the knee (eg improving tolerance to walking then maybe jogging) There is evidence that such programmes really do help both pain and function. Sometimes the addition of manual therapy (joint mobilisation by the therapist) can also be good but shouldn't be done without including rehabilitative exercise. One final component to consider: are you overweight? - great if you are not but even carrying a bit more weight than you should be greatly increases the damaging forces exerted on the knee when you walk. so your programme should include strategies to reduce weight that is a problem.
I suggest you find a good orthopaedic physio who can devise a gym based program for you. It won't change overnight - takes time and discipline - but give it a go. It could keep you fit and on your feet, thereby promoting good future health!