A therapeutic device which may be used in providing physical therapy for a patient's knee by moving the patient's leg through a plurality of cycles of motion in a treatment session. The device includes a “Fast Back” range of motion feature that permits the machine to be operated at more than one speed or rate per cycle, wherein the patient's knee may pass through a critical or working range of motion at a first rate, and through a non-critical or non-working range of motion at a second rate, so as to increase the portion of time of a treatment session that is spent in the working of the range of motion, as compared to conventional CPM machines. The preferred embodiment of the invention also has “soft turns” capability, wherein the carriage holding the patient's leg is decelerated, at a controlled rate over a controlled distance, from the operational speed to zero, as the carriage approaches an extension or flexion limit, and wherein the carriage is accelerated in the same fashion as the carriage moves away from the extension or flexion limit.