 The aim of the project is to compare the biomechanics of three different bearing designs used in total knee replacement TKR implants. The bearing is the part in the middle of the knee implant that allows the metal tray attached to the shin bone tibia to move in relation to the metal part attached to the thigh bone femur and is usually made of plastic high density polyethylene. There will be three different bearing types in the study, which all give different movements. This study will see which bearing is most like a natural knee and so which design gives the best function and feeling to patients with a TKR. 90 TKR patients from the Golden Jubilee National Hospital will be recruited and randomised to receive one of the three study bearings 30 in each group. In addition, a control group of 30 healthy individuals of similar age will be recruited for comparison. Before surgery and at 4 to 8 weeks and 1 year after their operation patients will attend biomechanical assessment sessions at the University of Strathclyde. The control group will attend the assessment session only once. In each of these sessions they will carry out a number of everyday tasks such as walking, moving from sitting to standing and going up and down stairs. These tasks will be measured using motion capture techniques. Reflective markers placed on each participant will be tracked by cameras so that their movements can be recorded. Force plates in the floor will record the forces during the tasks. 