Ultra-high molecular weight polyethylene (UHMWPE) is the material of choice in total joint replacement for hip cup and knee plateau because of its bio compatibility. The devices made of UHMWPE should be sterilized before implantation within the body and most reliable method for the purpose is gamma irradiation. However, sterilization with gamma rays generates free radicals which remained inside the crystalline core of UHMWPE. These radicals are the precursor of oxidation degradation of UHMWPE thus limiting the lifetime of artificial joints.We believe that, to eliminate these free radicals completely, researchers and peoples related with orthopaedic industry must have to understand the relation of residual radicals with three phase morphology (crystalline, amorphous, and interphase) of UHMWPE. For this purpose, in this book we have used different techniques such as ESR spectroscopy, wide angle X-ray diffraction, and Raman spectroscopy to have comprehensive understanding on the correlation of residual radicals with interphase contents of UHMWPE for vitamin-E blended UHMWPE. Moreover, a new way of enhancing the mechanical properties is also presented.