I have sudden pain in my knee from lifting foot from gas pedal to brake?

Lifting your leg up: like that uses the muscles on the front of your thigh (the quadruceps). It also causes the knee cap & knee joint to move. Any inflammation or irritation of these muscles or their tendons can cause pain. If the knee joint is rough, you can get pain in the joint or knee cap. If the pain is severe and/or persistent or becomes a problem during other activities, please see your doctor. Dr. Anne.

Tendon or meniscus: This could be related to a tendon issue surrounding the knee joint or it could be an internal issue such as a meniscus tear. If you have had no trauma to the knee it is less likely related to a ligament issue surrounding your knee. If the pain is along the inner knee under the knee cap it could be from the tendons in the inner thigh region.

Varies: The are several possibilities from quite benign to more serious. It could just be a aggravation of some underlying chondromalacia in your knee. Sometimes people can do what seems like a minimal action and get a meniscal tear as well, particularly if the meniscus is already somewhat degenerative. Don't hesitate to be seen for it.