Is the lotus position more prone to knee injury?

I've seen it mentioned once or twice, a great teacher or master who has knee injury due to lots of sitting practice. I know that if the posture is incorrect or if one is forcing it, it will lead to injury (I've read scary reports of people who permanently harmed their body because they tried it without proper guidance). But, seeing some teachers with such injuries as well made me wonder if even with a correct posture one may still harm its own body. I don't know if those cases I heard are exceptions (does anyone have seen other cases as well?). But, if this is because of *really* lots of practice, perhaps other "safer" postures could have prevented that? So, my question: given ideal conditions, such as correct posture and enough strength for it, is lotus position more susceptible to injury (in the long run) than other postures, such as burmese or half-lotus? Or, are all these injuries we see due to lacking necessary conditions? If someone could point me to a reference, that would be great.