The primary objective of this investigation was to evaluate & compare the performance of the P.F.C. Sigma Knee Cruciate-retaining all-polyethylene and metal-backed tibia components using RSA.

The secondary objectives of this investigation are to evaluate the clinical and patient outcomes and survivorship associated with the P.F.C. Sigma Knee Cruciate-retaining all-polyethylene and metal-backed tibia components.

Using RSA, is it possible to evaluate the performance of both the all polyethylene and metal backed tibia components to determine whether there are differences in migration, if present, across the tibial components.

The original protocol intended to perform clinical assessment using the Nottingham Knee Score and the Knee Society Clinical rating system pre-and post-operatively, at six months, 1 year, and annually thereafter. Per Protocol Amendment 01 (effective June 18, 1999) clinical data would also be collected via the SF-12 questionnaire. Radiological evaluation would also use the Knee Society scoring system at the same time points. However, data collected included only the SF-12 and Oxford Knee Scores, comparing change from baseline at 6, 12, and 24 months after surgery.

Inclusion Criteria:

• Subjects requiring a primary knee replacement.
• Subjects aged 65 years or more.
• Subjects who are able to give voluntary, written informed consent to participate in this clinical investigation and from whom consent has been obtained.
• Subjects with a primary diagnosis of osteoarthritis or rheumatoid arthritis.

Exclusion Criteria:

• Subjects who have had a previous surgery of the operative knee except menisectomy and arthroscopy.
• Subjects who have had a renal transplant.
• Subjects with a metabolic bone disorder.
• Subjects who, in the opinion of the Clinical Investigator, have an existing condition, e.g. Paget's disease etc. that would compromise their participation and follow-up in this clinical investigation.
• Subjects whose contralateral knee is already included in this study.
• Subjects who have a history of active joint sepsis.
• Subjects who have a recent history of high dose systemic corticosteroids.
• Subjects with psycho-social disorders or physical disabilities that would limit rehabilitation.
• Subjects requiring a bone graft.