Do any of you have any experience with any of the flexible types of stirrups? I've seen several in catalogues reputed to be helpful for riders with painful knees and ankles, etc. I have sometimes painful knees, ankles, hips, and lower back and can use all the help I can get! Right now I'm riding in regular fillis stirrups with pads. The flexible kinds are expensive but if they're worth it I might stretch to a pair.