Hello Anthony,
I'll give you the benefit of my experience. I'm 62, had bilateral knee replacement 4 years ago which has been very successful. I made a good recovery from surgery and began speed walking within a year, with little reaction other than some imbalance e in lower leg muscles. I was diagnosed with IgG MM in Sept 2011 (on my birthday!) and began treatment on Trial XI with Revlimid, Cyclophosphate and Dex in anticipation of an SCT and Melphalan. I'm at the QE in Birmingham under Prem Mahendra. During conditioning treatment with RCD I continued to walk although the speed and mileage dropped! I had a bout of pneumonia and cellulitis in Feb 2012 which meant me coming off RCD and then waited for SCT which I had in late May/June (4 weeks in the QE). I made a good recovery (complete response) and recommenced walking late last year; I now go out about 5 times a week and do 5 – 7 miles each time with both my knees and the rest of me doing very well apart from some issues with sciatica. It looks as though I'm relapsing at the moment (both my Paraproteins and Lambda Light Chain readings are climbing and I have some lesions in 2 of my vertebra) but I'm still walking and doing yoga stretches daily, which I intend to continue with as long as possible. My main (unresolved) issue at the moment is severe pain in the pelvis, buttocks and around the knees when I spend any time driving. I'm convinced that staying active is a key factor in combatting Myeloma, as well as my more mechanical issues! Tony, Solihull