Both knees have been replaced. When I fall I can not get up. I fell in the basement on the cement, and was not hurt but could not get up. No one was supposed to come here until 3: I fell at one. Just by chance, my son stopped in and got me up about one hour after I fell. I ordered the MobileHelp the next day. I feel more safe now, and I am very happy with it. I paid cash and got a wonderful discount. The neck piece is small and comfortable and they gave me a watch to wear at night. I am so happy with MovileHelp. They answer all my questions. I am so much more at ease when I am wearing my pendent.