Design: Prospective, case control Setting: subjects will undergo a tailored training program utilizing a novel biomechanical system comprising four modular elements attached onto foot-worn platforms (APOS system, Apos - Sports and Medical Technologies Ltd. Hertzlia, Israel) which conveys perturbation throughout the gait sickle. Pre and post training level walking will be examined via: (1) a three-dimensional motion analysis system and (2) ground reaction force analysis using force platforms (3) Electro-Myography system. Each subject will be examined in 4 different settings Patients will then participate in continued biomechanical perturbation training for 3-6 month and will then undergo a second gait examination Ages Eligible for Study: 50 Years - 75 Years, Genders Eligible for Study: None Accepts patients suffering from medial compartment knee osteoarthritis