Passive range of motion (PROM) is fantastic for supporting your dog's nervous system & joints! Motion is lotion for the joints, literally. Not only will you be helping the joints maintain some flexibility, you're also supporting the muscles, tendons, and ligaments that create movement withing those joints.
PLEASE CONSULT with your primary bodyworker and canine health team before attempting this exercise on your own. Your dog may not be a candidate or may require some adjustments to be made to suit their current health status and ability.