Update - I thought they has performed a MACI on my right knee but it was actually an ACI, according to the surgeon who told me this rather shocking fact it was up to individual surgeons preference as clinical outcomes, at least at Stanmore were not significantly different. The other thing to consider if more than one treatment option is available is which one is likely to work best for you, when you need it. Its fine to take part in an experimental trial but I find myself needing a knee replacement very soon but am leaning in the direction of going with a surgeon I know and trust rather than considering a potentially better treatment which is as yet unproven and the surgeon currently a total stranger.