I fell out of bed in 2012, hitting hard on right knee and then subsequently, the left knee. The floor is carpeted, but a cement based floor. Within seconds, two lumps appeared, the larger one on my right leg and a smaller one on my left. I used heat and ice packs, there was a terrible bruise and the darkened skin area have never disappeared. It no longer hurts. The swelling gets worse during the day and reduces a bit at night. I have asked several doctors what the problem could be and they all answered I don t know . It is an unslightly swelling, directly below the knee. A similar thing happened 42 years ago, when I fell and hit my left knee on a cement curb. The swelling from that one still exist, but does not bother me.