The physical therapist Is examining a rehab patient right knee in preparation for fitting them a knee brace. The patient is sat on flat and level treatment table so their right thigh is resting on the table and their right lower leg is hanging straight down off the end. The therapist manipulates the patients lower leg checking for flexion/extension range of motion. The therapist measures the angle between the athlete%u2019s thigh and lower leg at full extension and at full flexion. The right knee angle at full extension is 163.5degree and the right knee angle at full flexion is 83.3degree

What is the name of the anatomical plane in which this flexion/extension motion occurs.