TraceyW wrote:.....Colin: It feels like you are criticising me for wanting shorter cranks.....
Well, it was you that came on here asking for free advice; presumably you thought there might be people using this site who have more experience than you do?
My experience suggests you will be perfectly OK with standard length cranks, and my advice is that you should look elsewhere for a solution to your aches and pains. If you choose to interpret advice as criticism, that is your problem, not mine.
Bottom bracket bearing units come with a wide range of axle lengths....the length of axle you need is determined by what crankset you are using, and whether you want a road or an MTB chainline, so its pretty unlikely that any random chainset that you buy will need the same axle length as the unit fitted to your bike.