Total knee replacement, or total knee arthroplasty, is a highly effective surgical procedure that resurfaces a damaged knee joint with artificial components, known as prostheses. This intervention is commonly used to relieve pain and restore function in patients with severe arthritis. The decision to proceed with surgery is made only after non-operative treatments have failed to provide sufficient relief.
The procedure can be a Total Knee Replacement (TKR), replacing the entire joint, or a Partial Knee Replacement (PKR), replacing only one compartment. The optimal choice of implant is highly individualized, depending on patient anatomy, surgical technique, and design features. This article identifies the major companies and clarifies the criteria surgeons use to select the right device for each patient.
Identifying the Leading Implant Manufacturers
The global market for orthopedic implants is dominated by a few large multinational companies that consistently hold the largest market share. These corporations invest heavily in research, development, and surgical training, establishing themselves as primary suppliers. Their reputation is built on decades of clinical data and product innovation.
The four most dominant players in the knee implant market are Zimmer Biomet, Stryker, DePuy Synthes (a subsidiary of Johnson & Johnson), and Smith & Nephew. These companies collectively control a substantial portion of the orthopedic market, often estimated to be around 80% of the total. Each manufacturer offers a comprehensive portfolio of knee systems, including options for primary, revision, and partial knee procedures.
Zimmer Biomet is recognized for systems like the Persona and NexGen, while Stryker is known for its Triathlon knee system. DePuy Synthes markets the ATTUNE knee system, and Smith & Nephew features the Journey II and Legion systems. While product lines compete on features, these companies share a commitment to quality and innovation, including the integration of robotic-assisted surgical technology like Stryker’s Mako and Zimmer Biomet’s ROSA systems.
Key Factors Guiding Implant Selection
Implant selection involves technical, logistical, and non-technical constraints beyond performance alone. A primary consideration is the patient’s anatomy and expected activity level after surgery. Implants must be sized and contoured to fit the unique geometry of the femur and tibia to ensure proper joint mechanics and long-term stability.
Another determinant is the surgeon’s specialized experience and training with specific manufacturer systems. Orthopedic surgeons often develop high proficiency with one or two brands, as each system requires a specific set of instruments and a unique surgical technique. The surgeon’s comfort level with a particular system often dictates the brand used in the operating room.
Hospital inventory and standardization protocols also influence the final choice of components. Many hospitals negotiate contracts with one or two major suppliers to streamline inventory management and achieve volume discounts. This standardization means a surgeon may be limited to the implant systems stocked by the facility, even if they have experience with other brands.
Lastly, regulatory approval and long-term performance data play a considerable role in guiding selection. National joint registries track the long-term survivorship and revision rates of various implant models and brands. Surgeons rely on this peer-reviewed data to choose implants with a proven history of durability and low failure rates, prioritizing patient safety and the longevity of the replacement.
Differentiating Implant Materials and Designs
The physical properties and functional types of knee implants are the core differentiators between product lines. Metallic components—the femoral and tibial trays—are typically made from durable alloys, most commonly Cobalt-Chrome (CoCr) or Titanium. CoCr offers excellent wear resistance, while Titanium alloys are preferred for their flexibility and biocompatibility, often featuring a porous structure to encourage bone growth.
The bearing surface is made of ultra-high molecular weight polyethylene (UHMWPE). Advances in material science led to the introduction of highly cross-linked polyethylene (HXLPE), processed to reduce wear debris generation. While HXLPE demonstrated superior wear properties in hip replacements, its benefit in the knee joint is still under study, given the knee’s unique biomechanical forces involving both sliding and rolling.
Implants are fixed to the bone using one of three methods: cemented, cementless, or hybrid fixation. Cemented fixation uses acrylic bone cement to immediately secure the implant, which is advantageous for patients with lower bone density. Cementless fixation, also known as press-fit, relies on a porous metal coating that encourages the patient’s bone to grow directly into the implant, providing long-term biological fixation.
The most significant functional difference lies in the design philosophy, which determines how the implant interacts with the remaining ligaments. Cruciate-Retaining (CR) designs preserve the Posterior Cruciate Ligament (PCL), aiming to replicate natural knee motion, or kinematics. Posterior-Stabilized (PS) designs require the removal of the PCL and incorporate a mechanical post-and-cam mechanism. This mechanism substitutes the PCL’s function by preventing the thigh bone from sliding too far forward during bending, providing stability and controlling joint motion.