Risks of pedaling with outward pointing knee During my pedaling action I always try to keep my knee moving in plane parallel to the plane containing the frame, or, in other words, my leg parallel to the frame.

I have however noticed other fellow cyclists who tend to spread their knee outward during part or all of the pedaling cycle, like they are about to corner even though they are travelling straight.

Is it just a matter of esthetics, or is one of the two styles safer for joints/bones/muscles?

I am not asking why they do it (as in this question), but rather if it is neutral to the health of the cyclist.
I think this usually happens when people have the saddle extremely low. Having the saddle too low is bad for knees and power output.

According to my bike fitter a bit of sideways movement in the knees is not bad and mostly a matter of training (if your fit and shoes are otherwise okay). However, keeping it to a minimal is desirable and apparently some professional cyclists train this by strapping styrofoam to the sides of their frames.