Preventing Anterior Translation of the Human Knee Joint by Contracting the Biceps Femoris Muscle Using an Accelerometer and an Electrical Muscle Stimulator Device

This paper presents the design, implementation and the test results of a “Prophylactic Anti-Translational Electronic Knee Brace” which detects the abnormal anterior translation of the tibial bone in the knee joint caused by an anterior cruciate ligament rupture. With the help of a three axes wireless acceleration sensor, the agonist biceps femoris muscle is contracted in real time, using a microcontroller based electrical muscle stimulator (EMS), at the instant when the acceleration of the tibia exceeds a limit value. The waveforms of the modulus of the three axes acceleration components and the EMS pulses applied to the right and left knees of a healthy subject, during the extension and flexion tests on the knee joint are presented simultaneously and discussed. It was observed that, the EMS pulses are generated with a delay of 40 msec and contracted the biceps femoris muscle successfully, at the instant when the acceleration limit is exceeded.