Why I Use Kinematic Alignment in Knee Replacement

For decades, knee replacements were built on the idea that every knee should be perfectly straight. The trouble is, a lot of knees were never straight to begin with.

By Dr. Luc Rubinger, MD, MBA, FRCSC · Orthopaedic surgeon, hip & knee replacement · Durham Bone and Joint Specialists, Ajax · Last reviewed November 2026

The short version

  • Traditional mechanical alignment sets every knee to the same straight line, then adjusts the ligaments to fit.

  • Kinematic alignment rebuilds your knee to match how it was before arthritis, so your ligaments usually don't need adjusting.

  • The goal is a knee that moves, and feels, more like your own.

  • I use my own refined version, called iKA, which works with or without a robot.

The problem we're trying to solve

Knee replacement is very good at relieving arthritis pain. Even so, research over the years has found that roughly one in five patients isn't fully satisfied afterward. Often the knee is "fine," but it doesn't quite feel like theirs.

There are many reasons for that, but one leading theory is simple: we've been putting knees into a shape they never had.

The traditional way: make every knee straight

Since the 1970s, the standard has been mechanical alignment: make the leg a straight line from hip to ankle, with the knee joint sitting perfectly level. The engineering logic was sound: even loading across the knee joint should mean even wear.

But people come in different shapes. Most humans are naturally a little bow-legged or knock-kneed, and our knee joints sit at a slight angle, not perfectly level. To force those knees straight, the surgeon would often have to release (cut or stretch) some of the ligaments so the knee balances in its new shape.

The kinematic way: restore what was yours

Kinematic alignment flips the goal. Instead of imposing a new shape, I aim to restore yours. I remove the worn cartilage and a thin layer of bone, and resurface the knee joint with an implant of matching thickness. It's more like re-treading a tire than redesigning the car.

Because the joint ends up where it was before arthritis, your ligaments sit at their natural tension. In most knees, that means little or no ligament release is needed.

Why I choose it

  • A more natural-feeling knee. Restoring your own alignment aims to restore the way your knee naturally moves.

  • Your ligaments are respected. Fewer releases means more of your own knee left as it was, with less pain postoperatively, and a quicker recovery.

  • The evidence is encouraging. A growing body of research, including randomized trials, has found kinematic alignment performs at least as well as mechanical alignment, with some studies showing better function and satisfaction. Implant survival over the medium term looks comparable.

  • I've refined my own technique. I developed an approach using inverse kinematic alignment (iKA). During surgery, a tensioning device measures how your ligaments behave as the knee bends and straightens, and I fine-tune the plan to match. I designed it t reproduce robotic assistance with conventional instruments.

The honest trade-offs

  • Some knees need limits. If arthritis or your natural anatomy has created a severe deformity, I may set boundaries and bring the knee partway toward neutral. This is sometimes called "restricted" kinematic alignment.

  • Shorter track record. Mechanical alignment has decades of follow-up. Kinematic alignment's medium-term results are reassuring, but the very long-term data are still being collected.

  • Not every surgeon agrees. Alignment is an active debate in orthopaedics. I'm always happy to explain my reasoning and answer questions.

Common questions

Will my leg look bow-legged afterward?

If your leg had a slight natural bow before arthritis, the new knee will resemble that. It won't recreate the deformity that arthritis caused.

Will the implant wear out faster?

That was an early concern. So far, medium-term studies show survival comparable to mechanical alignment. I keep a close eye on the research as longer-term results come in.

Do I need a robot for this?

No. The robot adds precision, which helps, but the alignment plan is what matters most. My technique works with either.

Is kinematic alignment used for hips too?

Kinematic alignment is a knee concept. For hips, I use the anterior approach with X-ray guidance during surgery.

Related reading

Seeing Dr. Rubinger

I see patients at Durham Bone and Joint Specialists in Ajax, with surgery at Lakeridge Health Ajax Pickering Hospital and Schroeder Ambulatory Centre. In Ontario, you'll need a referral from your family doctor or nurse practitioner. Referral and contact information · Knee replacement overview.

This article is general information to help you understand your options. It isn't medical advice for your specific situation. Whether a procedure is right for you depends on an assessment by your surgeon.