Biomechanical dysfunction: The number of cases is staggering. Here's why

According to the American Academy of Orthopedic Surgeons (AAOS), more than 700,000 knee replacement operations performed each year in the United States.

Although the majority of these operations are performed in people over the age of 65, a growing number of knee replacements are being done in younger patients. A study presented at the 2014 AAOS meeting found that the number of surgeries for patients 65 to 84 increased by 89 percent, while surgeries for patients 45 to 64 increased by 188 percent.

Most surgeons expect to see the proportion of knee arthroplasties performed in younger patients continue to rise. One reason for this trend is improvements in surgical technique, as well as the design and construction of knee prostheses since the first knee replacement was performed in 1968.

Although most knee prostheses are still cemented in place, cementless prostheses were introduced in the 1980s. A second reason for the trend is people’s changing attitudes toward aging and their expectations of an active life after retirement. Fewer are willing to endure years of discomfort or to resign themselves to a restricted level of activity.

Why the Higher Numbers?

It is projected that the number of primary total knee replacements will increase to 3.48 million by 2030, compared with a growth in the number of primary total hip replacements to 572,100. Additionally, given the growth in the number of procedures in the younger, more active patients, implant longevity will require further enhancement.

These numbers are staggering, and they have to make you wonder: Why is this such a growing problem? Degeneration of the knees is not a new phenomenon to our society. I think the rate has been accelerated by the obesity epidemic in this country, as well as the fact that knee replacement technology has become advanced to the point that the risk of the surgery has been diminished by the reward of being pain free and active.

I have seen this with patients as well as family members—years of subtle biomechanical dysfunction leading to gradual degradation of the joint, followed by stiffness, swelling, and eventually debilitating pain. A vast majority of them responded favorably to the new hardware and were able to resume a more active and pain-free lifestyle.

The results are wonderful, but it still doesn’t make me a big advocate of knee replacement surgery. I am more of an advocate of common sense and conservative management, even going so far as to say that I am a “preventionist.” I am genuinely happy that there exists a technology for replacing damaged and degenerated joints—I just don’t want to participate in that technology. So I am going to take steps to prevent the factors that contribute to that sorry state.

Preventing Asymmetrical Stress Problems

To get my patients to understand the basic principles of prevention, I challenge them to think back to when they were 6 years old, and remember the old “Dem Bones” song. “The ankle bone is connected to the knee bone!” etc. It’s simple and a little silly, but truer words have never been spoken.

The foot and ankle influence movement and function throughout the entire skeletal structure. If there are subtle differences in function and flexibility from one foot to the other, those differences are translated superiorly through the knees into the hips, pelvis, and spine.

The most common influential factor of the feet is bilateral, asymmetrical excessive pronation. The dropping of the navicular bone and internal rotation of the foot/ankle complex slightly twists the knee—because the ankle bone is connected to the knee bone! The slight internal rotation of the tibia correlates with an increase in the Q angle.

An increased Q angle has been associated with increased incidents of ACL injuries, but let’s assume a patient doesn’t do anything very athletic that predisposes him or her to the running and jumping forces associated with a typical ACL tear. The difference is speed of injury.

The patient ends up with the slow accumulation of microtrauma as opposed to the sudden onset of macrotrauma. Asymmetrical stress to the cartilage is compounded by the fact that there is a neuromuscular inhibition of the quadriceps femoris muscle with excessive pronation, further contributing to the asymmetrical stresses on the knee.

This is the foundational source of stress that contributes to degenerative changes in the knees, hips, pelvis, and spine. For me, the most basic form of prevention comes from custom-made functional orthotics to block the biomechanical differences in the feet that are transferred up the kinetic chain.

Creating a symmetrical foundation at the feet with functional orthotics allows the joints above the feet to function more symmetrically. This reduces the effect of unequal forces and angulations on the cartilaginous structures and enhances the neuromuscular response to proprioceptive input.

When the harmful biomechanical stresses are managed efficiently, the result is a reduction in microtrauma. This means that there is less inflammation, scar tissue, and joint space degradation. Addressing the foundation is fundamental to preserving optimal joint function in the presence of an imbalanced foundation.

Brian Jensen, DC, graduated from Palmer College of Chiropractic in 1987. He speaks on a wide variety of topics, including orthotic therapy, posture, structural preservation, breaking free of the medical model of health care, and innovations in nutrition.

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