knee pain is a dull, aching pain that is most often felt:Behind the kneecap (patella)Below the kneecapOn the sides of the kneecapOne common symptom is a grating or grinding sensation when the knee is flexed (when the ankle is brought closer to the back of the thigh).Symptoms may be more noticeable with:Deep knee bendsGoing down stairsRunning downhillStanding up after sitting for awhileSigns and te