How the wear and tear theory is succumbing to muscle dysfunction research

We have all heard the argument that running is destroying our joints and that we'll all have arthritis during our golden years. Is this really true? Are we wearing out our bodies with the continual pounding of hundreds of thousands of foot strikes? Are we doomed to our fate?

Although there are many forms of arthritis, when we hear someone use the term they are likely referring to osteoarthritis, a painful, debilitating disease involving the degeneration of the weight-bearing joints of the body, such as the hips, knees and back. Often associated with impact exercise and activity, there are certainly outspoken critics who hold the "wear and tear" theory sacred and preach that by regularly running, we are all simply wearing out our knees and hips. However, this "gospel" simply doesn't hold true in the scientific literature. For years, experts in biomechanics believed it fundamentally true that the body deteriorates over time, and with the continual pounding of the lower limb during running (or other impact activity), it was inevitable degeneration would be the end result. That is, until more recent investigators decided to explore this "inalienable truth."

Wear and Tear versus Muscle Dysfunction
As a runner, you may be asking the question, "Why do I even care about osteoarthritis?" The answer is clear. For decades, researchers have suggested a link between exercise and osteoarthritis. Since osteoarthritis accounts for 90 per cent of hip and knee replacements, it behooves us to understand more about this ailment. And, if that is not enough, in 2008, the estimated annual cost for treating arthritis, its complications and resultant disabilities from the disease was $65 billion. Osteoarthritis has become an epidemic in today's society. We need to dispel the myths and learn the true nature of this common disease.

Many health professionals believed the major cause of primary osteoarthritis (excluding genetic disorders, severe biomechanical abnormalities, etc.) was "wear and tear" - that is, the gradual thinning of the articular cartilage due to repeated weight-bearing activity of the joints. The theory held that osteoarthritis is caused and worsened by activity. It wasn't until 1999 that this theory was challenged. A paramount review of the basic scientific literature proposed properly contracting muscles are the main shock absorbers for the joints, and muscle dysfunction is the most crucial mediating factor in causing osteoarthritis - not simple wear and tear from overuse.

This groundbreaking hypothesis, therefore, predicted exercise does not increase the likelihood of one developing osteoarthritis, or worsen it once developed! Why? Because exercise generally improves muscle function.

Basic Science Examined
It appears the scientific literature is now in strong support that regular mild-to-moderate-impact exercise does not increase the risk of osteoarthritis because of wear and tear on the body. Based on the principles of the wear and tear hypothesis, it's predicted that thinning of the articular cartilage (the smooth, glistening white tissue covering the surface of all joints) is the first sign of osteoarthritis. However, this is not the case. The opposing "muscle dysfunction" view is bone sclerosis (or thickening of the end of the bone) is the first sign.

The basic science implication leads to the conclusions that, when the muscles are not working ideally, the bone becomes more of a principal force absorber and is not able to absorb the impact the way it was designed to. Bone begins to thicken to compensate for the enhanced demand - sclerosis. Thus, bone sclerosis is the first sign of breakdown, with thinning of the articular cartilage not occurring until more advanced degeneration. In essence, the basic science tells us muscle dysfunction is the primary cause of osteoarthritis.

Translating Basic Science to Real Life
There are a myriad of scientific investigations into the body's adaptations to exercise as they relate to osteoarthritis. In fact, textbooks and scientific symposia have focused solely on this topic. Sports medicine physician and researcher Dr. Ian Shrier, in a systematic review of the scientific literature published in 2004, provides concise conclusions about the cause of exercise-related arthritis. He clearly demonstrates muscle dysfunction is overwhelmingly supported by the scientific evidence. The review reiterates the evidence supporting that moderate intensity impact sports do not cause or worsen osteoarthritis and that regular running with proper biomechanics increases the joint space - a finding opposing the concept of the wear and tear  theory. Finally, muscle dysfunction induces dynamic instability. This implies that, if the body is not moving efficiently, it becomes more unstable, negatively impacting joint health.

How do we translate this information into our everyday active lives so we can prevent breaking our bodies down? First, we must realize running and other impact activities do not cause joints to break down. This simply isn't true.

The key message is activity leads to joint health, given efficient movement and properly functioning muscles to absorb the impact forces associated with running. However, if our muscle function is compromised or our biomechanics are impaired, our body is unable to adequately absorb these impact forces. The result is gradual degeneration of our joints over time. This leads to osteoarthritis. Therefore, movement inefficiency is the real culprit. Numerous articles discuss this phenomena using terms such as biomechanical inefficiency, muscle-firing impairment, movement impairment, improper body mechanics and so forth. Although the nomenclature is not consistent, the message is clear - the goal is to achieve efficient and proper running mechanics and a balanced musculoskeletal system to fulfil a long and healthy running lifestyle.

Take Action
Have you ever wondered why one 70-year-old man is passing you in the local running race while another 70-year-old man is hunched over and inactive, telling you he stopped running when he was 40 because his knees gave out? Now we know - it's time to take action.

1. Stay active. We know running in and of itself does not cause the joints to deteriorate and will not end up making you an arthritis-ridden senior.

2. As a new runner, is your body prepared to begin a running program? A pre-activity physical assessment completed by your family physician is a must.

3. Prevent an injury from happening by critically evaluating your running ability. Is a 5K realistic for you? Is a marathon far-fetched? Too much, too soon leads to bad form and injury.

4. Get going with the right stride! Have a thorough running analysis completed by a professional knowledgeable in running and biomechanical analysis. This will allow you to develop a basic understanding of the biomechanics of running and to learn stretching, strengthening and technique tips specific to you.

5. Properly rehabilitate injuries. Get treatment. Studies tell us when we don't properly fix our injuries, we continue on with weak muscles or with improper mechanics. The result? Compensation in our running technique, breakdown and inevitable injury.

6. Listen to your body. Your body is always telling you how it's doing; are you listening? Modify your training schedule to promote efficient technique and healthy adaptation and to prevent inefficient running and injury. Cross-training activities such as biking or swimming are great ways to keep up your physiological/endurance training with less mechanical load on your joints.

Now we can dispel the myth that by simply running we're doomed to wearing out our knees and hips. We can tell those naysayers they're wrong! But, if we run improperly because of poor technique or because our body's muscles are not effectively working for any number of reasons, we're effectively in the same boat - breaking ourselves down. We've all seen those runners out on the pathways making it look like an onerous and painful task. They are running towards injury and osteoarthritis.

So, is running destroying your knees? The answer is a resounding - maybe! Treat yourself right - be an efficient and healthy lifetime runner.

About the Author

Dr. Greg Uchacz is a sports chiropractor and three-time Canadian Olympic Medical Team member. He is the director of the Chiropractic Performance and Sports Therapy Centre in Calgary.

"Does Running Destroy Knees?" first appeared in the 2010 July/August Summer Sports Issue of IMPACT Magazine.