Explaination for sudden surface bruise like knee pain very sensitive to touch which suddenly disappeared as if it was never there after odd move?

Varies: There are a number of possibilities if it became a problem that you are concerned about I would not hesitate to be seen. One possible cause can be plica syndrome, in which an abnormal band of tissue can cause the sudden onset of knee pain that could potentially be relieved by changes in knee position.

Loose body.: It could be a loose body floating around in the knee, which hides when you manipulate your knee a certain way.