I recently was bending down in my closet and while my knee was bent I banged the left side of my right knee on the corner of the wall. Now every once in awhile my knee will hurt when I go to bend it. I get a sharp pain in my knee when it happens on the left side of it. Or when I go to twist my knee a certain way. It will be fine for awhile and than it gets these spurts of it hurting. What could it be?