Study was terminated early due to prolonged recruitment period.

The purpose of this study is to evaluate if the P.F.C. Sigma RPF knee accommodates functional stability with a post-operative passive range of motion of greater than 125° of flexion and to demonstrate that the range of motion does not compromise the longevity of the implant.

Primary endpoint is to demonstrate that 90% of patients have a functionally stable knee that can achieve post operative range of motion of 125 degrees or greater.

The secondary endpoint is to investigate the survivorship of the P.F.C. Sigma RP-F knee at 1, 2, 3, 5, 10, 15 and 20 years

Inclusion Criteria:

• Male or female subjects, aged between 45 and 75 years inclusive.
• Subjects who are able to give voluntary, written informed consent to participate in this investigation and from whom consent has been obtained.
• Subjects who are able to achieve a pre-operative passive range of motion of equal to or greater than 110º.
• Subjects who, in the opinion of the Investigator, are able to understand this investigation, co-operate with the investigational procedures and are willing to return to the hospital for all the required post-operative follow-ups.
• Subjects who present with idiopathic osteoarthritis that in the opinion of the clinical investigator requires a primary total knee arthroplasty.
• Subjects who in the opinion of the Clinical Investigator are considered to be suitable for treatment with the P.F.C.® Sigma RPF knee, according to the indications specified in the package insert leaflet.

Exclusion Criteria:

• Subjects who, in the opinion of the Investigator, have an existing condition that would compromise their participation and follow-up in this study.
• Women who are pregnant.
• Subjects who are known drug or alcohol abusers or with psychological disorders that could effect follow-up care or treatment outcomes.
• Subjects who have participated in a clinical study with an investigational product in the last month (30 days).
• Subjects who are currently involved in any personal injury litigation claims.
• Subjects with a known history of poor compliance to medical treatment.
• Subjects who have a pre-operative limb deformity of equal to or greater than 10° varus or 15° valgus as defined using the anatomical axis.
• Subjects who have morbid obesity i.e. BMI ≥40.