A CPM chair for repeatedly flexing and extending a patient's knee permits a patient to remain comfortably seated while controlling therapeutic knee flexure and extension. A slide member is longitudinally reciprocal between extended and retracted positions with its slide direction controlled by the patent. A drum has an endless cable wrapped about its periphery and is rotated in alternate directions by a reversible electrical motor. The cable extends over respective forward and rearward pulleys and is secured to the slide member. A pedal assembly supports the patient's foot and is pivotally secured to the slide member to accommodate different positions of the patient's heel. Control switches are actuable by the patient to control slide member direction.