scrubbing hardwood floor on knees two weeks ago. Have had bad pain in left knee, lower right section of the knee above shin. At first thought a very bad deep bruise, but is no better after two weeks. Limping, difficulty on stairs or steps, hurts all the time but has periods where more severe than other times, very painful to touch, but localized, just started swellling (not hugely swollen) yesterday. Any ideas what this is and why not getting better? Thank you.