I used to have some Shimano SPDs and found them difficult to get out of. Fiddled with the settings but no luck. Also, had an ACL replaced plus not much cartiledge in left knee. The movement necessary to unclip from the SPDs (slight twist outward) was especially difficult given the knee issue. Eventually, I gave up on them and on the idea of clipping in. I've been looking at the Speedplay Frog (since it is the only one that can be used on an MTB shoe). Reviews claim they are good for folks with bad knees and that clipping in and out is easy. Would appreciate input from anyone with them (or Speedplay in general). Three questions: 1) Are they as kind to the knees as advertised? 2) Are they easy to get out of (but hold the foot firmly when riding)? 3) Do you get hot spots due to the small platform size? Vielen Dank.