This book presents a comprehensive, state-of-the-art review of the latest progresses in UHMWPE biomaterials, which has been critical for the performance and longevity of joint implants. Oriented by clinical challenges to UHMWPE-based joint implants, it introduces the processing, crosslinking, structural manipulation, oxidation mechanism, stabilization, drug delivery, and wear, as well as clinical performance, biomechanics, and simulated studies of joint implant based on UHMWPE with low wear, which are aimed to tackle or minimize the adverse effect related to wear and wear debris. These contributions provide fundamentals of chemistry and physics of UHMWPEs to help understand the clinical performances of UHMWPE based joint implants. Perspectives to next generation UHMWPE to meet the unmet challenges in clinical use are included.