Polyethylene bearing failure has been cited as one of the leading causes of knee arthroplasty revision surgery. In 1998, highly cross-linked polyethylene was introduced for clinical use in total hip arthroplasty. Altered mechanical properties in first-generation highly cross-linked polyethylene did exhibit clinical failures, such as post fractures in total knee arthroplasty. Remelting alters the integrity of polyethylene. Some approaches to mitigate this include mechanical deformation, vitamin E incorporation, and sequential irradiation and annealing. Forces and stresses in total knee arthroplasty differ substantially from the wear mechanisms and forces seen in total hip arthroplasty. There is now considerable interest in the clinical use of highly cross-linked polyethylene for the knee. The use of sequentially annealed, highly cross-linked polyethylene, based on bench top data, appears to be promising for use in total knee arthroplasty. One should be aware that all highly cross-linked polyethylenes are not manufactured, nor processed, in the same manner. Marked and significant differences may exist between products.