Functional outcome will be assessed by recording the kinematics of the lower limb joints in addition to muscle activity (electromyography) during walking, stair ascending and descending and getting up from a chair through computerized 3D motion analysis. Outcome measures will be recorded immediate post surgery and at medium follow-up and will cover all areas of the World Health Organisation, International Components of Functioning, Disability and Health (ICF) components 'Body Structures and Functions/Impairments' ,'Activities and Participation' and 'Personal factors'. It is hypothesized that by minimizing the damage to the quadriceps, patients operated using the Mid-vastus approach will have better muscle function and will therefore have more normal knee range of motion, knee joint loading and muscle activity patterns compared to those with the Medial Parapatellar approach.