For decades, knee replacement surgeries have utilized a one-size-fits-all method, following a standardized technique known as mechanical alignment.
This process positions knee implants in a straight, consistent line between the hip, knee and ankle, passing through the center of the knee. While mechanical alignment helps distribute weight evenly across the knee joint, possibly leading to the longevity of the implant, it ignores one crucial factor: a patient’s natural anatomy.
As a result, orthopedists have begun to explore an alternative approach known as kinematic alignment.
What is kinematic alignment?
Ortho One
Dr. Robert N. Steensen
Kinematic alignment, unlike mechanical alignment, aims to duplicate the position of the patient’s own, unique joint surfaces, restoring the knee’s natural, full range of motion prior to developing arthritis.
“The results of (the) mechanical alignment technique have been pretty good… but as with any endeavor in medicine, we’re trying to continually improve,” says Dr. Robert N. Steensen, an orthopedic surgeon and founding member of Orthopedic ONE. “Kinematic alignment is personalized. Just like people are different sizes and shapes, they have legs that have slightly different alignments too, and kinematic alignment tries to match their alignment to respect their natural anatomy.”
By replicating the knee’s unique angles and joint lines, kinematic alignment may lead to a more natural-feeling knee replacement, allowing the knee to move more smoothly and improving function.
Kinematic alignment also eliminates the need to release ligaments during surgery, which otherwise could impact the knee’s stability and function.
“In a way, you could say mechanical alignment is making the knee fit the technique or the implant, whereas (with) kinematic alignment, we’re making the technique fit the bones,” Steensen says.
This is achieved partially thanks to updated tools, including a flexible instrument set known as MicroPort Kinematic Alignment set. These tools allow doctors to dial into the knee at any given angle when previous instruments were only able to cut into the bone at a standard angle.
“I’ve been involved with kinematic alignment for 10 years, and when I first looked around, there weren’t instruments that I felt were to my satisfaction. So, I helped design some instruments,” Steensen says. “I’ve used those instruments for seven years now, and I’ve been very pleased, I’ve seen the benefits.”
Dr. Steensen
Benefits
In addition to surgical improvements, kinematic alignment offers additional longer-term benefits.
Thanks to the better fit achievable through the procedure, patients also experience less pain after their implant, recover faster, return to everyday activities sooner without complication and maintain stable results long after surgery.
“It’s a newer approach, but it’s gaining popularity in an almost exponential way, and I think that’s because the results are seeming to be improved over mechanical (alignment),” Steensen says.
Multiple studies have shown promising results through short- and long-term analysis of kinematically aligned implants and patient-reported outcome measurements.
One study, published by the National Institutes of Health, found a significant improvement in patient-reported outcome measurements, with a sharp drop in pain levels within the first three months of receiving an implant. Patients also reported their new knees felt more natural over time, with satisfaction scores improving steadily between three months and two years.
That same study also found no risks of implant failure or second surgery from malalignment and reported no detriments to implant longevity.
To help patients better understand why kinematic alignment can be so beneficial, Steensen likes to use a simple analogy.
“If you had a flat tire, you would take it off and put a new wheel exactly where it was, right? You wouldn’t say, ‘Let’s move it a half inch forward,’ because then it wouldn’t line up with the axle,” he says. “The knee has an axis of rotation (too), and when we do kinematic (alignment), we’re trying to match that axis of rotation.”
Dr. Steensen
Improvement, not replacement
While yielding favorable results, it is important to note that kinematic alignment is unlikely to completely replace the use of mechanical alignment.
“Mechanical alignment (is) a good thing, (it) has done wonders for people. This is more of a tweaking… ‘Can we make it better?’” Steensen says.
Both techniques have strengths and weaknesses, and the optimal choice is ultimately contingent upon each individual patient’s anatomy.
“If somebody’s leg was pretty straight already… they may not notice much of a difference,” Steensen says. “But if somebody was, for instance, a bit bowlegged, and you restored them back to the way they were before… they may feel better with that knee than they would if (it) was made perfectly straight.”
Still, Steensen wishes to see continued research involving the alternative technique, viewing it as contributive toward perpetual growth within the orthopedic field and, ultimately, better patient recovery.
“The goal is to give them pain relief and restore their function and stability so they can forget they had a knee replacement,” Steensen says.
Dr. Steensen’s General Tips for Knee Health
Ortho One
- Watch your weight. A substantial amount of excess weight can put stress on the joints.
- Maintain your strength. Regular strength training is not just beneficial for the knees and joints, but also crucial for overall health. To strengthen muscles around the knee, try exercises such as squats, lunges, hamstring curls, calf raises and straight leg raises.
- Tailor your activities. If your usual exercise begins to trouble your knees, consider switching to low- or non-impact activities such as walking, cycling, swimming, yoga or Pilates.
- Consider past injuries. A knee injury, even in youth, can increase the risk of needing a replacement later in life. Consult your doctor sooner rather than later if experiencing troubles.
Ella Jay is an assistant editor at CityScene Media Group. Feedback welcome at ejay@cityscenemediagroup.com.
