Actually, SC, he was very much out and about all over London, on foot, without any appearance of difficulty (of course he might have had the good pain killers). He had the surgery some time before the show, btw, not after. Furthermore, the promoters at Montreux apparently knew well beforehand that Pagey wasn't going to show, and the knee thing was indeed the 'spin'. That is the actual story--I was there (at Montreux and in Selfridges!!).
Edited to add: and don't get me wrong, I'm sure Jimmy had his own good reasons for not wanting to be there.