I had right knee pain walking downstairs which happened 3 weeks ago. I am a competitive marathon runner, 49 year old female, and have run 23 marathons to date with no knee pain ever. Both knees now feel dull and I have random twinges in my right knee when I sit. I have a race on Sunday, and I am uncertain if I should do it. I have cut my mileage as this is the taper time frame, iced both knees regularly and used a foam roller on my quads to speed recovery. I had a random buckling of my right knee on my run on Tuesday in the 1st 50 meters and then it subsided after I shook the knee out and it did not hurt thereafter. (This was a 3 mile recovery run.)