The aim of this study was to design and manufacture a Mechanical Knee-Hip Strengthening Device (M K-H SD). The device was designed in Catia software. Then, a laboratory sample was made according to the designed sizes. Special features of the device include adjusting the knee range of motion between 20˚ of extension to 120˚ of flexion to reduce of the stress on the patellofemoral joint, adjusting the hip range of motion between 30 degrees of flexion and 20 degrees of extension in proportion to thehip angles in a normal walking cycle, increasing the force of isotonic contractions by changing the number and stiffness of the springs, maximum voluntary isometric contraction at the end of 20˚ of extension and 120˚ of flexion. The M K-H SD is recommended instead of quadriceps chair due to its affordable, more efficiency (knee and hip joints) and control of the knee painless range of motion.