Design and Testing the Continuous Passive Motion Device for Knee Rehabilitation

Abstract

          Objective: The continuous passive motion device is used to increase knee range of motion after a total knee arthoplasty. Since the restricted range of motion affects functional activities, this research work aimed to the design, construct and test the continuous passive motion device for knee rehabilitation after surgery. The chosen design incorporates a slider crank linkage mechanism as it offers a range of motion similar to the natural variation of the knee angle during activities in daily life.

          Methods: The continuous passive motion device in this research consisted of a 5.4 V 1.4 A DC step motor, a microcontroller, a motor driver, a slider crank linkage mechanism part, and a ball screw. A ball screw with a pitch of 0.01 m and 0.5 m length was driven by motor. The motor was commanded from motor driver controller and micro controller. The device enabled extension and flexion of the knee joint within the range of motion from 0 degree to 90 degree at speeds of 5, 6, and 7 mm/s. The digital goniometer was installed on the pivot joint on the linkage mechanism to measure the knee angle movement compared with the predetermined angle movement at that angle to find the percentage of error of the knee angle movement.  

          Results: From the test, it was found that the continuous passive motion device can function as intended and it was able to move according to the preset angle and speed accurately. The percentage of error of the movement and velocity were in between 0.05 to 2.70 percentages and 0.20 to 1.60 percentages, respectively.