I had bad knees for years, but found that running exclusively up-hill on uneven ground for about 2 years completely cured them. This might not be practical or

I had bad knees for years, but found that running exclusively up-hill on uneven ground for about 2 years completely cured them. This might not be practical or work for you, but I found a steady improvement after I started walking gently down hills and only running up. I also made a conscious effort to minimize the impact of each footfall. After 2 years, I found I could even run downhill again without pain or injury.