Runners and Knee Osteoarthritis

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Original Editor - Kapil Narale

Top Contributors - Kapil Narale and Lucinda hampton  

Introduction

Running has become an increasingly popular activity, and form of exercise, throughout the world, over the last few decades. Although injuries are possible, there are many health benefits to running. However, there is a large misconception that running may lead to osteoarthritis, and it is very uncertain whether running has a detrimental effect on the knees . In fact, there is evidence to prove that the pinion of running causing osteoarthritis is not correct.

As mentioned on the Osteoarthritis page, osteoarthritis is a degenerative condition. It affects the joints, cartilage, bones, tendons, and ligaments. Its main cause its linked to metabolic and systemic conditions, such as hypercholesterolemia, hypertension, and high blood glucose levels, to name a few. Individuals can be asymptomatic, thus would only be diagnosed when they notice symptoms such as joint line tenderness, reduced range of motion, crepitus with movement, joint effusion, and/or joint space deformity, and seek medical attention.

Benefits of Running

Some noted benefits of running, as found from studies of runners and non-runners include,

• Decreased risk of cardiovascular disease
• Decreased risk of Type II Diabetes
• Decreased risk of depression
• Decreased prevalence of disability and mortality
• Positively affects bone mineral density, and weight control

The rate of disability and mortality is much lower in runners, compared to non-runners. It was also noted that running can increase longevity, through an increase in muscle strength, cardiovascular reserve, bone mineral density, and glucose tolerance.

In addition, runners generally have a lower body mass index than nonrunners. This can be seen to act as a protective mechanism towards knee osteoarthritis.

Knee Biomechanics with Running

As mentioned above, the peak joint force on the knee is much higher in running than walking, roughly 3 times as high.

It is interesting to note that the peak knee joint loads exceed the threshold that would lead to osteoarthritis. This threshold is ironically also exceeded in walking, and thus runners would be expected to develop knee osteoarthritis. This expectation or belief is in fact false, for the following reason.

It would be noted that with running, there is a much shorter contact time with the ground, and most of the time is spent in swing. This in turn, minimizes the effect of the high peak joint forces experienced at the knee. For this reason, it is seen that the peak joint load, and duration becomes equivalent to that of walking.

The loading response of articular cartilage depends on the peak load, as well as loading rate and duration. The joint loads from running can be beneficial for preventing knee osteoarthritis, compared to a sedentary lifestyle.

The peak load on the knee, and the impulse on joint contact force, increased with an increased running speed. Therefore it is possible that the runner can increase their training speed, without increasing their risk of osteoarthritis.

Factors Associated with Osteoarthritis

Some intrinsic risk factors for developing osteoarthritis include:

• Age
• Gender
• Genetics

Extrinsic modifiable risk factors include:

• Previous injury
• Activity level
• Occupational tasks
• Obesity

Sports, such as soccer or football, which involve repetitive, high impact, torsional forces, are more likely to lead to osteoarthritis. Previous injuries to muscles, joints, ligaments, tendons, can also increase the likelihood of osteoarthritis.

It is seen that an increase in body mass has a direct effect on osteoarthritis. As one's weight increases, the biomechanics of human movement alters, as the loading surfaces of articular cartilage in weightbearing joints. For instance, with a single-leg stance, an increase in 1lb of bodyweight increases the loading on the knee by about 2-3lbs.

Reducing/Modifying OA factors

In overweight individuals, osteoarthritis symptoms can be more effectively prevented or minimized by the use of exercise and diet, instead of solely modifying their diet.

Running and Injuries

Similar to any activity, running does not come without any risk of injury. Infact, knee and ankle injuries are quite common, which generally occur due to overuse, and can cause injuries such as patellofemoral pain syndrome, iliotibial band syndrome, or achilles tendonitis.

Factors which can increase in the likelihood of injury include, increasing age, being female, improper running gait and mechanics, training volume, muscle strength, and having a previous injury.

Running and Osteoarthritis - Evidence

It is important to note that running can load the joints as much as eight times more than walking. As activity progresses, and muscle capacity decreases due to fatigue, the apparent loading can be even higher.

This is not to say that joints shouldn't be loaded, and loading is not good, since moderate loading is required for articular cartilage health.

There is little evidence which demonstrates that running causes osteoarthritis. Despite running being repetitive, with an increase in joint loading, the runner does not experience excessive torsional loads, and a risk of traumatic injuries to joints and ligaments. This is mor likely experienced in soccer players, and weightlifters, as there is a higher evidence shown on radiographs, compared to long-distance runners.

A longitudinal study over 8 years has shown that recreational runners, or runners over 50 years of age, shows that there is no radiographic clinical evidence leading to knee osteoarthritis.

A study comparing runners and nonrunners which analyzed bone mineral density in the spine, hip osteoarthritis, and knee osteoarthritis, noted that there was higher bone mineral density in runners. Despite this, there were no differences, or presence of, osteoarthritic qualities such as, joint space narrowing, crepitation, or joint instability.

With these findings, various researchers and authors have concluded that running does not increase the risk of developing osteoarthritis, over the long term.

The National Runners and Walkers Health Study in 2013, analyzing over 89000 runners, including marathon runners, showed that running does not increase the risk of osteoarthritis. This study also showed that running decreases the risk of osteoarthritis, and hip replacement, due to the lower Body Mass Index (BMI) of the running population.

Changes in cartilage, before and after running, were assessed using magnetic resonance imaging (MRI). Characteristics such as cartilage volume, compression, and thickness, under loads, were assessed using T1- and T2-weighted MRIs.

• T1 weighted images - these facilitate viewing of the proteoglycan matrix of the cartilage, and acute fluid changes. THis owul dbe helpful in determining long-term changes in the cartilage. Signs of early stages of osteoarthritis would be indicated by a decrease in the matrix.
• T2 weighted images - these indicate water and collagen content in the cartilage. This would help determine short-term changes in water content and fluid balance.

Cartilage is seen to have a beneficial effect with moderate exercise, though cannot be confidently extrapolated to high-volume, marathon, runners.

However, another study showed that runners, having run three marathons or less in their lifetime, may experience negative long term biomechanical changes to articular cartilage. This was seen with long term changes in the T1 imaging, while T2 imaging returned to normal subsequent to three months. An MRI was taken immediately post-marathon. Changes were noticed in T1 and T2 imaging upon MRI, but the T1 imaging remained altered subsequent to three months.

Another study showed that there were no changes in bone marrow edema, joint effusion, or periosteal reactions, between pre-marathon and post-marathon MRIs. It was concluded that long-distance running does not lead to internal stresses on bones and joints.

From a study conducted examining the radiographic images of recreational runners compared to nonrunners, of mid-to older-age adults, it was concluded that there was no evidence to suggest that general runners in the community have an increased risk of knee osteoarthritis, compared to nonrunners. When analyzing running activity at different life stages, leisurely running did not pose a risk to prevalence of knee pain, radiographic osteoarthritis, or symptomatic osteoarthritis. The study even found that runners experienced less knee pain than nonrunners. However, another study claims that runners are not at a greater or lower risk of knee osteoarthritis, compared to nonrunners.

Knee pain and symptomatic osteoarthritis were least observed in current runners, and is most common in those who do not run at all.

Limitation

A limitation to a such study which assessed individual's current knee pain status as a result of running through different phases of their life may have a limitation in that people may have stopped running due to the experience of knee pain in the past, and aren't current runners anymore.