I put my foot on a folding chair and was tying my shoe laces tighter, and stood up and lost my balance before lifting my foot from the chair. I fell against a piece of furniture and hit the closet door and landed my butt on the floor. I figured that when I landed on the floor, my foot was still sort of on the chair, so my leg was sort of straight out when I landed. Now my calf area below my right knee is very stiff and hurts somewhat to walk. I had this knee replaced back in 2004 and was told that I had a lot of arthritis within the legs. I am almost 71 years old. I am suppose to see my doctor on this coming Friday for a back problem I am having. Back does not hurt me right now. Not sure how I will feel in the morning.