sounds like you are not absolutely sure you can blame your injury on clipless. If it were the case , could be use of fixed clips have been too limiting on needed knee/ankle rotation.
I have used clipless for years. Can't imagine difficulties caused by clipless. I feel more secure in clipless. When riding platforms, I feel as if i might loose control of my bike, since a slip off the pedals could cause one to loose control of the bike.
With a short commute on flat terrain, I am sure platforms work out just fine. But, being clipped in, it gives me far more options in terms of like standing on hills, when I need a little more power. On platforms, I'd never get out of my saddle. I would not like that.