The aim of the study is to assess the performance of the cementless Triathlon Tritanium tibial baseplate for total knee replacement, with a minimum follow up of 5 years.

All potential total knee arthroplasty patients from two consultant orthopaedic surgeons at the Golden Jubilee National Hospital (GJNH) will be screened in relation to the inclusion/exclusion criteria. Invitation letters and participant information sheets (PIS) will be sent out to suitable patients who have been referred to the GJNH for total knee replacement (allocated patients) prior to their pre-operative consultation with their surgeon. They will be approached at their consultation visit to seek consent to take part in the study. Patients who have been referred to the GJNH for assessment for a knee replacement (see and treat patients) will be approached only if they are deemed eligible for knee replacement by their consultant, and will be given a copy of the participant information sheet along with the invitation letter. They will be approached for consent to take part in the study at their pre-operative assessment. All patients will be given the opportunity to ask questions about the study before signing the consent form. Consent will be taken by the chief investigator or their delegate, using a signed form.

One hundred patients will be recruited to the study. They will have their surgery performed by one of the participating consultants using the study implant, the Triathlon Tritanium cementless tibial baseplate manufactured by Stryker Corporation.

Participants will receive their standard in-patient care and rehabilitation. Standard hospital care for knee arthroplasty patients is for them to return to the hospital for a post-operative review at 6 weeks and then 1 year and 7 years after operation. Study participants will also be asked to attend the GJNH for two additional research specific appointments at six months and five years. They will be also contacted by post or via telephone to complete a study questionnaire (patient satisfaction) at 3 years post operation.

During the standard care appointments, patients will be reviewed by a member of the arthroplasty team who will collect routine data on the clinical and functional outcomes and implant stability. These data include the Oxford Knee Score (OKS), EURO Quality of life questionnaire (EQ-5D 5L), patient satisfaction and standard radiographic assessment of the implant.

Detailed radiographic analysis will be carried out on radiographs collected as standard and specifically for the study. These will be post-operation at day one (standard), 6 weeks (standard), 6 months (study), 1 year (standard) and the 5 years (study) time points. Study specific radiographic assessment will consist of assessment for radiolucency and osteolysis at specific regions around the tibial and femoral components. Pre-operatively, a standard weight bearing long- leg anterior-posterior (AP) view, lateral view and a skyline view is obtained as per standard care. Post-operatively, standard care consists of a standard weight bearing long-leg AP radiograph at 6 weeks and a short AP and Lateral view at all other reviews.

Study participants will also have two sessions of specialised functional assessment (biomechanical movement analysis and 6-minute walk test) before operation and 1 year after operation during their standard pre and postoperative visits. Biomechanical movement analysis will be carried out in an on-site movement analysis laboratory. Study participants will be required to wear suitable clothing (e.g. tee shirt and shorts) and be barefoot. A number of reflective markers will be attached to specific locations on the body using suitable double sided tape which can be tracked by a number of infrared cameras. participants will be asked to perform the following tasks; walking, stepping up, stepping down, sit-to-stand, stand-to-sit and single leg balance. Each task will be performed at least three times to enable the collection of three good sets of data. In addition, the two stepping tasks will be repeated for each limb. The single leg balance will be performed once for each leg and data will be collected for 30 seconds per limb. A motion capture system will collect limb and torso movements during the task performances while force plates will collect ground reaction forces. The 6-minute walk test requires the participant to walk around a course during a six minute period. They are allowed to have rest breaks for as long and as often as they require. They will be asked to stop walking six minutes after the start of the test and the distance covered during the period will be noted.

Inclusion Criteria:

1. Unilateral TKA
2. Age 18-75 years
3. BMI <40
4. From one of the following health boards: Ayrshire & Arran, Forth Valley, Greater Glasgow & Clyde, Highland, Lanarkshire or Lothian
5. Suitable to receive the study implant

Exclusion Criteria:

1. Revision of existing knee replacement
2. Previous hip or knee replacement surgery if within the last 12 months
3. Previous ankle surgery
4. Diagnosed osteopenia or osteoporosis
5. Proximal tibial bone defects
6. Unable to give informed consent
7. Unwilling to take part
8. Unable to return to the Golden Jubilee National Hospital for followup appointments

Patients who have been referred to the Golden Jubilee National Hospital for total knee replacement.