I live on Kodiak, and my knees are crap. One ACL replacement and both menisci are torn. I do a lot of strength training, particularly the legs, and it makes a world of difference. Squats, lunge jumps, burdened hiking - whatever your toture de jour happens to be. Work, work, work! Leg strength and cardio.
Trekking poles are a biiiiiig help if you use them properly. Use the tops of the poles in your palms going down hill, and plant and pull going up. Use your upper body as much as possible, it's not doing anything much, anyway. I do about 800 mg ibu twice a day, and try to empty my 100ml water bag over the course of the day.
BTW: Bears are not some malevolent monster. Most of the DLP kills are from people who panic after watching too many reality shows. Ascribing some evil intent causes unnecessary problems.