This study evaluates outcomes of robotic-arm assisted mechanically aligned total knee arthroplasty [MA TKA] versus robotic-arm assisted functionally aligned total knee arthroplasty [FA TKA]. Half the study will receive MA TKA and half will receive FA TKA.

Total knee arthroplasty [TKA] is an estabilshed treatment for symptomatic end-stage knee osteoarthritis, but there is a higher disatisfaction rate when compared to total hip arthroplasty. The exact aetiology of this is not clear but recent studies have shown one possible reason to be conventional TKA with mechanical alignment [MA] may force the knee into an unnatural position. This may lead to altered knee anatomy and kinematics that may compromise patient satisfaction.

Total knee arthroplasty using functional alignment [FA] aims to restore the patient's prearthritic knee anatomy and native joint kinematics. Early clinical and functional outcome studies have reported promising outcomes in TKA with FA but results of longer term studies have not yet been published.

There are very few prospective studies exploring clinical and radiological outcomes in MA versus FA for TKA. It is possible to improve on previous studies by recording a more comprehensive range of clinical and functional outcome measures, blinding patients and observers recording outcomes of interest, and using longer follow-up times.

Robotic-arm assistance can be used to improve the accuracy of implant positioning. Clinical and functional outcomes should also be correlated to longer-term outcomes to better establish the "safe zone" for functional alignment. The findings of this study will enable an improved understanding of the clinical and functional benefits of FA compared to MA. These outcomes will improve our understanding of the optimal TKA alignment with possible improved outcomes; improved cost-effectiveness by reduced revisions and better patient satisfaction and function; and improved long-term implant survival.

100 patients will be enrolled in a 1:1 ratio between the two treatment groups. Trial patient will be allocated to either the MA TKA ['Control group'] or to the FA TKA ['Investigation group']. Outcomes will be recorded at specific milestones.

Inclusion Criteria:

• Patient has symptomatic knee osteoarthritis requiring primary TKA
• Patient and surgeon are in agreement that TKA is the most appropriate treatment
• Patient is fit for surgical intervention following review by surgeon and anaesthetist
• Patient is between 18-80 years of age at time of surgery
• Gender: male and female
• Patient must be capable of giving informed consent and agree to comply with the postoperative review program
• Patient must be a permanent resident in an area accessible to the study site
• Patient must have sufficient postoperative mobility to attend follow-up clinics and allow for radiographs to be taken

Exclusion Criteria:

• Patient is not suitable for routine primary TKA e.g. patient has ligament deficiency that requires a constrained prosthesis
• Patient has bone loss that requires augmentation
• Patient is not medically fit for surgical intervention
• Patient requires revision surgery following previously failed correctional osteotomy or ipsilateral TKA
• Patient is immobile or has another neurological condition affecting musculoskeletal function
• Patient is less than 18 years of age or greater than 80 years of age
• Patient is already enrolled on another concurrent clinical trial
• Patient is unable or unwilling to sign the informed consent form specific to this study
• Patient is unable to attend the follow-up programme
• Patient is non-resident in local area or expected to leave the catchment area postoperatively

No plan