My Miyata 1000 LT had Biopace and killed my knees. Replaced them with round and my knees still don't like it, but didn't hate it as much. No idea why—it's supposed to be a very comfortable bike, the geometry is the kind I like, I'm a pounder more than a spinner (and it's caught up to me with hypermobile joints, so I've been spinning more than I used to), I tried far more saddle positions than I did with any other bike, it's the right size, and it's made of nice steel. And, yes, I'm getting older, but my 1912 Iver is more comfortable even though the saddle is a little low (can't go higher). Anyway, I can't completely blame the Biopace, but it definitely made it worse. I would have thought this square thing was a joke if I saw someone riding with it.