For decades, total knee replacement has been one of the most successful procedures in orthopedic surgery — with over 600,000 performed in the U.S. each year. But here’s something most patients don’t know: not all knee replacements are aligned the same way.
The traditional approach, called mechanical alignment, targets the same “textbook” straight line from hip to ankle for every patient — regardless of how their knee was actually built. It works. But about 20% of patients remain dissatisfied with the result. Their knee functions, but it doesn’t feel right.
A different approach — called kinematic alignment — is changing that.
What Is Kinematic Alignment?
Kinematic alignment was pioneered by Dr. Stephen M. Howell, an orthopedic surgeon and researcher at the University of California, Davis. The concept is deceptively simple: instead of forcing every knee into the same alignment, restore the knee to the way it was before arthritis damaged it.
Your knee has three natural axes of rotation — the way it flexes, extends, and rotates. In a healthy knee, these axes are aligned with your natural joint line. Arthritis destroys the cartilage, but the underlying architecture of the knee — the ligaments, the bone geometry, the way it was designed to move — is still there.
Kinematic alignment preserves that architecture. The surgeon cuts bone to restore the natural angle and level of the joint line, rather than imposing an artificial one. The result: the implant sits where the original knee surface was, and the ligaments don’t need to be released or “rebalanced” to make it work.
How Is This Different From Traditional Knee Replacement?
In traditional mechanical alignment, the surgeon cuts the bone perpendicular to the mechanical axis — a straight line from the center of the hip to the center of the ankle. This sounds precise, but it changes the natural angle of the joint line. To compensate, ligaments often need to be released or tightened to “balance” the knee around its new, artificial geometry.
Even Dr. John Insall, who helped establish mechanical alignment as the standard, described it as “a compromise.”
Kinematic alignment takes a fundamentally different approach:
- Mechanical alignment: Makes the knee fit the implant
- Kinematic alignment: Makes the implant fit the knee
By restoring the natural joint line, kinematic alignment minimizes the need for ligament releases. In Dr. Howell’s experience with over 2,800 consecutive patients, collateral ligament, retinacular, or PCL release was rarely required.
What Does the Research Show?
The evidence supporting kinematic alignment continues to grow:
- Level 1 evidence (the gold standard — a double-blind randomized controlled trial) showed that kinematic alignment provided significantly better patient satisfaction, function, and flexion compared to mechanical alignment
- Patients averaged an Oxford Knee Score of 42–43 out of 48 (near-perfect function)
- At 3-year follow-up, there were zero catastrophic failures — even in patients whose components were in positions traditionally considered “outliers”
- The technique minimized undesirable contact kinematics (edge loading, abnormal rotation), suggesting excellent long-term durability
- Results were consistent across multiple surgeons, confirming the technique is reproducible
Why Does This Matter to You?
If you’re considering knee replacement, alignment matters more than most patients realize. A knee that’s aligned to match your anatomy — not a textbook average — is more likely to:
- Feel natural from the start
- Achieve better range of motion
- Require fewer ligament releases during surgery
- Result in higher satisfaction scores
This is especially important when combined with robotic-assisted technology, which allows the surgeon to execute a kinematic alignment plan with sub-millimeter precision. At Movement Orthopedics, we use the VELYS™ robotic-assisted platform to deliver patient-specific kinematic alignment for every knee replacement.
A Note on the Evidence
We believe in transparency. Current research shows no statistically significant difference in clinical outcomes between robotic-assisted and conventional total knee replacement. Robotic technology improves component positioning accuracy, but the outcomes advantage comes from the alignment philosophy — kinematic vs. mechanical — not the robot itself. The robot is a precision tool that helps us execute the plan more reliably.
The Bottom Line
Knee replacement has come a long way. The question is no longer just “should I get a knee replacement?” — it’s “what kind of knee replacement gives me the best chance of a knee that feels like mine?“
Kinematic alignment, backed by Level 1 evidence and over 2,800 consecutive patients in Dr. Howell’s series, offers a compelling answer: restore the knee nature gave you.
To learn more about our approach to knee replacement at Movement Orthopedics, or to schedule a consultation, call (586) 436-3785 or book online.
Reference: Howell SM, Roth JD, Hull ML. Kinematic alignment in total knee arthroplasty: definition, history, principle, and results. Arthropaedia. 2014;1(1):44-53.