The Three Pillars of Total Knee Arthroplasty and Alternative Alignment Strategies

Total knee arthroplasty has been an extremely successful surgical procedure and has offered great benefit to millions of patients. Surgeons and implant designers continue to strive for the perfect or “Forgotten” total knee. The goal is to have the replaced joint feel and function like the pre-arthritic joint to the patient.

The three pillars of total knee arthroplasty are implant design, technique, and technology. Implant design has been a major focus through the years. The two main traditional designs, cruciate retaining (CR) and posterior stabilized (PS), have different philosophies but appear to have similar results. Medial pivot designs have been available for many years but have recently gained much greater interest. Medial pivot implants have a philosophy of trying to match the medial stability and lateral mobility of the native knee.

Techniques are evolving as well. Mechanical alignment (MA) has been the standard for many years but alternative alignment strategies are viewed by some as a way to improve clinical results even further. The techniques differ in philosophy and what they prioritize. MA strives for a straight hip–knee–ankle (HKA) angle and the joint line perpendicular to that line. Ligaments are released to obtain symmetric flexion and extension gaps. Alignment is the priority. The alternative alignment strategies that have emerged, most notably kinematic alignment (KA), are individualized to the patient. The goal of KA is to place the implant to restore the pre-arthritic joint surfaces. The priority is restoring the surfaces and native balance. Unrestricted KA does this alone, while restricted KA places limits or borders on the patient's deformity that will be accepted and outliers will be brought back within those limits. Functional alignment (FA) uses advanced technology to achieve patient-specific balanced flexion and extension gaps.

Technology progresses over time. Manual instruments are still the most widely used. Navigation and patient-specific instruments were tried but did not make great inroads. Currently there is interest in robotics but improved patient outcomes have not yet been seen. There are now advanced manual instruments that allow restricted KA.

The options in implant design, technique, and technology are greater now than in the past. Philosophies can change over time. Is it more important to have a straight HKA angle or match the patient's native alignment? If performing KA, should there be limits? What might those limits be? Should the flexion and extension gaps be symmetric since the native gaps are asymmetric? With a systematic technique such as MA, results could be reported as one group. As a more personalized approach is possible, it will be important to report results in subsets to see if all or some subsets fare well. It will be with further study that the ideal combination or combinations will optimize patient outcomes. As in Bayesian convergence, as time progresses and more is known, the approaches will converge to a more and more common ground.

This is an exciting time in total knee arthroplasty as the different philosophies will be tested. I thank the distinguished authors of the articles in this Special Focus Section on Kinematic Alignment in Total Knee Arthroplasty in The Journal of Knee Surgery.

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Artikel online veröffentlicht:
06. Juni 2025