Check the car seat. It must be too low, the butt is lower than the knee, and the driver’s seat is either too forward or too far back. There are two positions of the knee that will lead to pain when one presses on the gas pedal. (1) The knee is too high and the butt is too low. I call it the newfangled back-killing driver’s bucket seat. It is a bucket, not a seat! Throw away the car and get a truck, an SUV or take the bus. Never buy a small car with a driver’s side bucket seat. If one insists on buying a small car, find one that does not have a driver’s side bucket seat, although they may be harder and harder to find nowadays. Go for a mid-sized car instead. Many mid-sized Toyotas, Volvo, luxury BMWs, Audi, Volkswagen, do not have driver’s side buckets (seats). (2) The seat is too far back, the right leg is almost straight and the knee flat. When one pushes the foot forward to press the gas pedal, the foot muscle and the leg muscles including the calf muscles and the hamstring muscles are stretched in this position. After driving for long distance with the right leg “stretched”, any movement of the foot, like pressing forwards, pulls the leg and knee muscles.
In both cases, the knee will hurt.
Again, throw away the dinky little car with that newfangled bucket as the driver’s seat, walk, take a bus, get a mid-sized vehicle that does not have a bucket as the driver’s seat, or get an SUV or a pickup truck.
If one prefers driving a luxury car, get a European model. If one prefers a Cadillac, make sure to raise the seat to its maximum height and adjust the yaw of the seat so that the knee and the butt are at level.