Total Knee Arthroplasty (TKA) is the surgical reconstruction of the knee joint in order to relieve pain, restore function and correct deformity. It is a very common surgical procedure with figures showing more than 500'000 arthroplasties performed annually worldwide. Total knee arthroplasty is considered one of the most successful types of joint reconstruction in that surgical results usually meet and even exceed expectations. Much of the current literature focuses on the issues relating to implant wear as a potential failure mode for artificial knee implants. It has been suggested that knee with mobile or rotating bearing options, such as the comparative device proposed for this clinical investigation, may survive longer than fixed bearing knee designs because of the greater contact surface area possible with more congruent components with unconstrained, mobile component design.

This is a prospective, comparative, randomised, open-label, single center, multiple surgeons clinical study. The Scorpio PS Superflex and the Scorpio PS mobile bearing are to be implanted for evaluation in this study. Patients will be randomised to one of two equal sized groups. In the first group patients will be treated with the Scorpio PS Superflex, whilst in the second group patients will be treated with the Scorpio PS mobile bearing implant.

Evaluations consist of the KSS score, Chair rise and stair climb tests, radiology assessments, patient questionnaires, at multiple timepoints: pre-operative, 6 weeks, 3 months, 6 months 1 year, 2 years and 5 years post-operatively.

Inclusion Criteria:

• Patients requiring cemented primary total knee replacement.
• Patients with a diagnosis of osteoarthritis (OA), avascular necrosis (AVN) or post-traumatic arthritis (TA)
• Patients who understand the conditions of the study and are willing and able to comply with the post-operative scheduled clinical and radiographic evaluations and the prescribed rehabilitation.
• Patient who have intact collateral ligaments.
• Patient who signed the Ethics Committee approved specific Informed Consent Form prior to surgery.

Exclusion Criteria:

• Patient where patella will not be resurfaced.
• Patients with active or suspected infection.
• Patients with a diagnosed systemic disease that would affect the subject's welfare or overall outcome of the study (i.e. severe osteoporosis, Paget's disease, renal osteodystrophy) or is immunologically suppressed, or receiving steroids in excess of physiologic dose requirements.
• The patient has a neuromuscular or neurosensory deficit which would limit the ability to assess the performance of the device or the patient has a neurological deficit which interferes with the patient's ability to limit weightbearing or places an extreme load on the implant during the healing period.
• Patients, who as judged by the surgeon, are mentally incompetent or are unlikely to be compliant with the prescribed post-operative routine and follow-up evaluation schedule