In my 27.5 years of car ownership, I've owned two Toyota Tercels and my current Honda Fit -- all manual transmission (MT). I've owned my 2013 Honda Fit (Canada) for 6 years, and I find that the way the clutch pedal swings downward close to the floor requires one to unhinge one's ankle, sort of pointing one's toes, in order to fully depress the pedal. At the same time, I need to contract muscles in the butt and lower back to ensure the leg is delivering the force downward.
When I first drove the Fit, I found that this unfamiliar motion quickly caused some knee pain. I've since found ways to mitigate it by ensuring that my leg is positioned slightly to the outside, and the foot angled inward a bit when pressing the pedal. But it still causes problems that I further mitigate with cold compresses every night.
I suspect that the main source of my problem is that unhinging of the left ankle so that I'm tippy-toe-ing the pedal (or rather, using the ball of the foot), while extending my leg and using butt and lower back muscles to maintain downward pressure is an exacerbating factor. It's a rather awkward move. Perhaps the amount of attention given to the design of the clutch pedal was limited because of the limited market size? MT has become quite rare in North America.
My left leg is my good leg, and I keep reasonably fit with low impact strength exercises. I don't normally consider that limb to be predisposed to this kind of problem.
I'm wondering how systematic the problem is. Am I an oddball in finding this problematic, or is it more widespread? I'm not sure how easy it is to get an idea of this from responses, given the miniscule portion of the market that is MT.
As well, I suspect that it is unrealistic to have the pedal modified? It would be changing a key part of the design, and I wouldn't really know how to spec out a better design. It seems like changing cars would be more feasible.