Swollen knees and swollen ankles are usually indications of edema. The most common occurrence of swollen ankles and swollen feet often happens after sitting in the economy class seat on a flight of three hours or more. A similar situation would apply after driving for a length of time. The legnth of time for the knees to become swollen would be directly related to the duration of the trip and the driver’s seat. A newfangled deep spoon shaped bucket seat that devastates the lower back will shorten the duration for the knees to become swollen.
Again, throw away the car and get a car that is taller than you with an adjustable square driver’s seat like the seats that are installed in big pickup trucks, large SUVs or get a 1950s Cadillac or Buick that has a bench seat in front.