Department of Mechanical Engineering, Stanford University, Stanford, CA, USA e-mail: avikr@iiitdm.ac.in

design strategies, and patient-specic considerations. The clinical impact and regu­latory standards governing these prosthetics are also examined. Various musculo­skeletal conditions related to bones, including osteoporosis, bone cancer, congenital anomalies, war-related injuries, and unexpected incidents, collectively result in a yearly economic burden of $136.8 billion on the United States economy. The review further classies types of hip and knee replacements, including total hip replace­ment (THR) and resurfacing hip replacement (RHR). It underscores the clinical signicance of wear and friction in these contexts. Types of wear in knee and hip joints, such as adhesive, abrasive, fatigue, and corrosion/oxidative wear, are dis­cussed, along with materials selection for implants, encompassing metallic, ceramic, polymer, and composite options. Various surface modications for enhancing wear resistance are also explored, including ion implantation, surface coatings, and bio­mimetic modications. Lubrication strategies in hip and knee replacement, the role of synovial uid, and lubrication techniques in articial joints are reviewed along­side emerging surface coatings for wear resistance, such as hydroxyapatite, diamond- like carbon, and metal nitride coatings. Experimental approaches to wear and friction studies, including pin-on-disk testing, joint simulators, tribo-corrosion testing, and wear debris analysis techniques, are analyzed, with a focus on future directions and emerging technologies like additive manufacturing, smart implants, biomaterial innovations, and articial intelligence in wear prediction. This review concludes by summarizing the current state of knowledge in wear and friction mechanisms in knee and hip rehabilitation and outlines future research directions in this critical area.

Since its initial use, hip prosthetic design and material development have advanced steadily. In implant technology, its development is one of the century’s most dif­cult problems. The rst hip operations were performed in England in 1750 to treat cases of arthritis [1]. Early hip prostheses were made from wood, ivory, and natural polymers like rubber. These tended to have poor durability and integration. This treatment was terrible since the body was exposed to wear particles. The earliest suggestion for treating a hip injury was to replace it with a prosthesis in 1840 [2, 3]. It was only possible to replace or resurface the acetabular portion of the femoral head during this treatment. A decade later, around 1930s–1950s, stainless steel, cobalt-chromium alloys and polyethylene became more commonly used in hip implants, though longevity was still a problem. In the 1960s–1970s titanium alloys were introduced. Titanium had improved biocompatibility and corrosion resistance compared to earlier materials. In the 1980s–1990s ceramic materials like alumina and zirconia were explored as alternatives to address wear and durability issues.