Knee replacement surgery, formally known as knee arthroplasty, exchanges damaged joint surfaces with artificial components. This procedure is primarily performed to alleviate chronic pain and restore mobility in patients whose knee cartilage has been severely compromised, most commonly due to advanced arthritis. The operation involves resurfacing the ends of the thigh bone (femur) and shin bone (tibia) with metal and plastic implants shaped to allow smooth, continued motion. Total knee replacement is regarded as one of the most successful surgical treatments available, offering significant pain relief and functional improvement. The journey to this highly refined procedure is a complex history of innovation, material science, and surgical technique.
Precursors to Joint Replacement
Before the concept of a true prosthetic replacement emerged, surgeons in the 19th and early 20th centuries attempted to treat debilitating knee arthritis by either fusing the joint or placing material between the damaged surfaces. One of the earliest approaches was arthrodesis, which intentionally fused the bones of the joint to eliminate movement and, consequently, the source of pain. While this technique provided reliable pain relief, it permanently sacrificed the joint’s function and mobility.
Another early idea was interpositional arthroplasty, where various substances were inserted between the worn ends of the femur and tibia to create a new, smooth surface. Pioneers experimented with a wide array of foreign materials, including pig’s bladder, fascia, cellophane, glass, and ivory, attempting to prevent the two bones from rubbing against each other. German surgeon Themistocles Gluck, for example, experimented with rudimentary hinged joints made of ivory. These early attempts were hampered by high rates of infection, mechanical failure, and limited long-term success.
The Landmark First True Knee Replacement
The first truly pivotal step toward modern knee replacement occurred in the mid-20th century, drawing inspiration from the success of total hip replacement, which utilized metal and plastic components fixed with bone cement. The first successful total knee prosthesis that was not a highly constrained hinge design was the Polycentric Knee, developed by Dr. Frank Gunston, a Canadian orthopedic surgeon. Gunston designed and performed the procedure around 1969, publishing his work in 1971.
Gunston’s design was revolutionary because it was a bicompartmental resurfacing arthroplasty, replacing the surfaces of both the medial and lateral sides of the joint. The implant used separate cobalt-chrome metal tracks cemented onto the femur and opposing polyethylene components cemented onto the tibia. This approach successfully applied the principles of low-friction arthroplasty to the knee, using the durable metal-on-plastic combination proven in hip surgery.
The Polycentric Knee design aimed to mimic the complex rolling and gliding motion of the natural knee, a concept known as polycentric motion, rather than simply acting as a mechanical hinge. This was a significant departure from earlier, highly constrained hinge implants, which often failed due to the high stress placed on the components. Gunston’s innovation marked the beginning of a new era, establishing the foundational design philosophy of a prosthetic joint that resurfaced the worn surfaces and was fixed to the bone using polymethylmethacrylate (PMMA) bone cement.
The Development of Modern Total Knee Arthroplasty
Following Gunston’s pioneering work, the 1970s became a period of rapid evolution, leading to the standardized procedure performed today. The key to this development was the shift from the Polycentric design to the total condylar prosthesis, which resurfaced the entire end of the femur with a single, articulating component. A significant breakthrough came with the introduction of the Total Condylar Knee in 1974, developed by Dr. John Insall and colleagues at the Hospital for Special Surgery.
The Insall-Burstein design, and similar total condylar systems, standardized the surgical technique by requiring precise, simple bone cuts and utilizing a single femoral component and a single polyethylene tibial component. These implants were made from durable, biocompatible materials like cobalt-chrome alloys for the metal components and ultra-high molecular weight polyethylene (UHMWPE) for the plastic bearing surface. The standardization of these components and the surgical approach dramatically improved reliability and long-term outcomes, leading to the widespread adoption of total knee arthroplasty.
Further advancements focused on implant mechanics, transitioning from constrained designs that sacrificed the posterior cruciate ligament (PCL) to modern posterior-stabilized (PS) and cruciate-retaining (CR) designs. PS knees incorporate a cam-and-post mechanism to replace the function of the PCL, while CR knees preserve the patient’s ligament. More recently, improvements in material science have led to highly cross-linked polyethylene, which offers greater wear resistance and extended implant longevity. The procedure continues to evolve with the use of cementless fixation techniques, which encourage the patient’s bone to grow directly onto the porous surface of the implant.