I am experiencing that right now. I have been gimping around for two days. I work at a rehab, and a few of the therapists suggested maybe a tear. My kneecap feels like the top half is going east, and the bottom is going west, and it is extremely painful . I can't put any weight on it or turn it in a certain direction. I am going for an MRI, and I'll let you know the results. FYI....I did not injure my knee, it could just be a case of wear and tear.