Validation of TKA Easy software: Are the clinical outcomes the same as the TKA 4.3 software?

INTERVENTION: All patients will undergo a primary navigated TKA. Patients will be assessed at the pre‐operative clinic, and an Oxford Knee Score will also be taken as part of their routine clinical care. The study will be discussed. Following consent the patient will be randomised using sequentially numbered, opaque sealed envelopes (SNOSE) 8. The research coordinator (or nominated person) who will be independent of the approach and consent of the patients to the study will name, sign and open the envelope and inform the study team of the randomisation. One group (Easy) will be randomised to the OrthoPilot TKA easy application. The second group (4.3) will be randomised to the former version of navigation software (TKA 4.3). The patient will then undergo a navigated TKA as normal. The prosthesis used will be the Columbus knee prosthesis which is normally used by both surgeons in the study. This prosthesis holds a CE certification and is a class III medical product. Passive trackers will be used in both treatment groups irrespective of the software being used. In both cases the standard software will be used. This will exclude use of the software that allows for a soft tissue balancing procedure. The registration time will be automatically recorded by the software. The total operation time will be defined as the 'skin to skin' time and will be recorded by an independent theatre person who is not involved in the study. The surgeon will not be made aware of the operation time until the end of the surgery to decrease the risk of bias. For this purpose theatre clocks will be covered. The patient will be seen post‐operatively during their inpatient stay and followed‐up at six weeks. At six weeks they will have a Computerised Tomography (CT) scan of the knee (using the Imperial knee protocol ) instead of the routine hip‐knee‐ankle X‐ray to determine the alignment of the prosthesis. The total effective dose for this protocol has been calculated by the Radiation Protection Adviser an CONDITION: Navigated Total Knee Arthroplasty ; Musculoskeletal Diseases PRIMARY OUTCOME: The overall lower limb coronal alignment (mechanical femorotibial angle) as measured on the post‐operative CT scan SECONDARY OUTCOME: 1. Radiological ‐ Component alignment and rotation and sagittal lower limb alignment; 2. Patient reported outcome measures ‐ Oxford knee score and Patient Satisifaction; 3. Clinical outcomes ‐ Knee Society Score, range of motion, number of complications; 4. Operative times ‐ registration time and overall operative time INCLUSION CRITERIA: 1. Patients having a primary navigated knee arthroplasty 2. Able to give informed consent 3. Able to return for follow‐up