Hi Gaz, it could just be an age thing, it could be a weight thing - I get an occasional painful left knee and for the past few years have had painful shins when running, playing football, etc but NOT when cycling which is partly why it is now my exercise of choice! I think my weight contributes to it as well. Also you mentioned being on standard flat pedals, one thing I've noticed since going clipless is how straight my feet feel (weird at first) and how the feet point "outwards" with anyone who is not clipless - may just be your body adjusting to the new exercise regime! It does get harder as you get older, unfortunately. Regards, Mark