Help for leg pain/mobilty

Hello my 86 year old mom needed knee replacements years ago which she refused to have. As a result her legs, calves mainly, stiffened up and walking is very hard for her now. She was making some improvements with swimming, a hot tub, and rowing but with the pandemic her gym shut down and she’s lost strength and her walking has deteriorated. On FB I saw ads for various products — one with compression massagers that wrap around the feet and calves (slabway.com) and the other with pedals that move your feet and ankles while sitting (legxercise.com) I just found out she has one of those whole body vibration machines (one of my brothers recently bought one used but she hasn’t used it yet) you can stand on so wondering if anyone has experience with those either. Any comments and suggestions are welcome