Knee Pain (diff knees/diff pain!)

In right knee at the back is painful when running. I always warm-up & stretch & have tried some self massage. Any ideas?
Left knee – fell badly on the outside 3 wks before xmas. All brusing/swelling now gone but when I do breaststroke it is painful on the inside, as if something isn’t sitting right. The more breaststroke I do it eases off so maybe I just need to do some physio/strengthening exercises? Any ideas? Appreciated.