Polyethylene is used as the liner in both knee and hip replacements. The plastic is extremely strong and wear resistant, but often, if a joint replacement becomes loose, it's because of wear of the polyethylene. One of the techniques we use to strengthen the plastic is to radiate it causing the molecules of the plastic to crosslink together. This makes the plastic stronger, but also more brittle. To offset this problem, the plastic we use is treated with Vitamin E during manufacture. Vitamin E is a natural antioxidant and prevents the increased brittleness of the plastic. I think this will result in less wear of the plastic and longer lasting knee and hip replacements. Plus it looks much prettier in yellow.
Dr. Barry Waldman