Can croc shoes cause foot, ankle, knee injuries?

Not usually: No more than any other shoe. Your shoes need to be fit properly to your foot. Many people with foot problems find crocks to be comfortable and wide enough for their feet and to accomodate their foot problems.

Crocs are: For the most part very comfortable. There are medical versions which are a bit more supportive. I'd suggest that they are less likely to cause injury than the omnipresent flip-flop.