Jul 21 • Dr. Stephen Howell, MD

Medial or Lateral? The Native Knee Pivot Controversy and Its Implant Consequences

The debate over medial pivot versus lateral pivot knee implant design is a hot topic in total knee arthroplasty (TKA). While some surgeons embrace the lateral pivot concept, decades of biomechanical research tell a different story.

In this edition of the KA-Optimized Editorial, Dr. Stephen Howell examines the evidence behind the native knee pivot, explains why much of the lateral pivot literature is misunderstood, and discusses how these findings should influence implant design in kinematic alignment (KA) total knee arthroplasty.

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Key Takeaways

  • The native knee demonstrates a medial pivot throughout the functional arc of motion (20°–120° of flexion).
  • The key measurement for determining the center of rotation is the differential in anterior-posterior (AP) translation between each femoral condyle.
  • Studies reporting a lateral pivot primarily evaluated ACL-deficient knees, reconstructed knees, osteoarthritic knees, or analyze the native knee with clinically important measurement limitations.
  • Multiple modern gait and fluoroscopic studies of the native knee consistently demonstrate a medial pivot during functional activities.
  • Implant designs that combine a flat lateral compartment with a conforming medial ball-in-socket better reproduce the medial pivot of the native knee even after ACL removal.
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Why the Medial vs. Lateral Pivot Debate Matters

The debate isn't simply about where the knee pivots—it's about accurately restoring native knee motion after total knee replacement.

Dr. Howell explains that the key measurement is the difference in anterior-posterior translation between the medial and lateral femoral condyles, not the location of a single pivot point. Through the functional arc of motion, modern biomechanical studies consistently support a medial pivot pattern.
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Bottom Line:

Current evidence supports four conclusions:
  1. The native knee pivots medially during functional activities.
  2. The strongest evidence for a lateral pivot comes from altered knees or studies with methodological limitations.
  3. Restoring native knee mechanics requires understanding condylar motion—not simply identifying a pivot point.
  4. Implant designs that restore medial stability while allowing lateral motion most closely replicate native knee kinematics after TKA.
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Freeman MAR, Pinskerova V. The movement of the normal tibio-femoral joint. J Biomech 2005;38(2):197–208.

Gray HA, et al. Three-dimensional motion of the knee-joint complex during normal walking. J Orthop Res 2019;37(3):615–630.

Thomeer LT, et al. Articular contact motion at the knee during daily activities. J Orthop Res 2022;40(8):1756–1769.

Rao Z, et al. In vivo kinematics and ligamentous function during weight-bearing flexion. KSSTA 2020;28(3):797–805.

Nicolet-Petersen S, et al. Small differences in tibial contact locations after KA TKA. KSSTA 2020;28(9):2893–2904.

Koo S, Andriacchi TP. The knee joint center of rotation is predominantly on the lateral side. J Biomech 2008;41(6):1269–73.

Hamilton LD, et al. Knee pivot location in asymptomatic older adults. J Biomech 2023;149:111487.

Simileysky A, Hull ML. Tibial contact points cannot be used to determine axial rotation. The Knee 2024;51:145–152.

Kozanek M, et al. Tibiofemoral kinematics and condylar motion during the stance phase of gait. J Biomech 2009;42(12):1877–84.

Morishige Y, et al. 4DCT analysis of screw home movement in the ACL-deficient knee. Skeletal Radiol 2022;51(8):1679–1685.

Elorza SP, et al. A new tibial insert with ball-in-socket medial conformity and PCL retention. J Exp Orthop 2023;10(1):115.

Howell SM. Medial or Lateral? The Native Knee Pivot Controversy. J Orthop Exp Innov. In press.

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