Osteoarthritis is an affliction whereby the articular cartilage present in the joint space starts to progressively degrade, causing mild to excruciating pain (depending on the stage of osteoarthritic joints) and severely affecting mobility and the quality of life of patients. Advanced stage osteoarthritic joints need a surgical intervention in the form of total joint replacement (TJR) as a ‘cure’. TJRs encompass total knee replacements, total hip replacements, total shoulder replacements, and more. Ultra-high molecular weight polyethylene (UHMWPE) has been used as a bearing material in TJRs for over six decades owing to a slew of attributes it exhibits including but not limited to exceptional energetic toughness, mechanical integrity, and biocompatibility. However, given the hostile environment that the orthopedic grade polymers experience in-vivo, there are reports of TJR failure induced through wear (caused by the constant articulation of the mechanical components in TJRs), fatigue (owing to the cyclic nature of biomechanical stresses), and corrosion (given the saline ambience inside the body). Consequently, new polymer bearing materials like Polyether ether ketone (PEEK) and PEEK composites are increasingly being explored in the orthopedics community to overcome the aforementioned challenges. Alongside, there is a push towards improving the surface attributes of the TJR components given that wear, fatigue-induced wear, and corrosion are primarily surface and sub-surface phenomenon, and researchers in this field are looking into varied surface modification techniques from plasma surface treatment to coatings to post-processing and compositional changes through alloying to address persistent problems with TJRs.

This thesis delves into the bio-tribo-mechanical characteristics of both of these orthopedic-grade polymers, namely, UHMWPE and PEEK. First, an overview of the fatigue of polymers with special focus on UHMWPE is provided to lay the groundwork. Next, a deep dive into the tribological, mechanical, and biocompatibility aspects of PEEK and its composites is undertaken and their suitability for use in TJRs as a potential substitute for UHMWPE is thoroughly understood. Thereafter, some initial findings concerning the fatigue crack initiation phenomenon in UHMWPE from clinically relevant stress concentrations in TJR components like notches are duly reported. Finally, a perspective on bringing about a fundamental shift in the orthopedics realm by employing surface modification techniques such as Diamond-like Carbon (DLC) overcoats on TJR components to mitigate problems such as wear, corrosion, and metal-ion release plaguing modern-day TJR systems is discussed for future researchers interested in this field.