Purpose: The purpose of this study is to compare the clinical results of a standard polyethylene tibial insert versus the high flex polyethylene tibial insert component designs of a posterior cruciate substituting total knee replacement.

Method: One-hundred patients were entered into a prospective, randomized clinical trial comparing standard polyethylene tibial inserts versus the high flex polyethylene tibial insert component designs of posterior cruciate substituting total knee replacement(Genesis II, Smith & Nephew, Memphis, TN). Patients were evaluated pre-operatively, at 3, 12 months and annually thereafter. Patient demographics, radiographs, and multiple outcome measures (WOMAC, SF-12 and the Knee Society Clinical Rating System) were evaluated.

Results: No patients were lost to follow-up. One patient died prior to the two year follow up. Ninety- nine patients were reviewed at an average follow-up of 2.7 years (range 2.3 – 3.1 years). There were no significant differences in any outcome measures or radiographic findings. There were no differences in KSCRS at two years (Standard − 170, High Flex −171). There were no differences in knee flexion at 2 years (Standard− 125°, High Flex − 126°).

Conclusion: In this prospective randomized clinical trial, no differences could be seen between standard polyethylene and a “Hi- Flex” polyethylene design at a minimum of 2 years follow-up. In particular, no improvement in knee flexion was observed. Long-term evaluation will be required to comment on differences in polyethylene wear and implant longevity.