Oh, those achy knees! That’s what millions of people over the age of 50 say on a frequent basis. Chances are, those achy knees are due to knee osteoarthritis, a degenerative type of arthritis that becomes increasingly common after the age of 50.
Osteoarthritis is due to cumulative joint injury and damage or “wear and tear.” That’s why symptomatic osteoarthritis is more common later in life. However, injuring a ligament, joint, or joint cartilage can hasten the onset of osteoarthritis in that particular joint. Even poor posture plays a role by placing excess stress on the joints.
Arthritis of the Knees and Cumulative Stress
One of the most common places people develop arthritis is the knees. No wonder! Your knees are exposed to constant stress, including the burden of carrying around your own body weight. According to Harvard Health, the force on your knees when you walk on a flat surface is about 1.5 times your body weight. If you walk on an incline, such as up a hill, this increases the stress on your knees to 2 to 3 times your body weight. Finally, if you go up a flight of stairs, the force on your knees is magnified by 4 to 5 times your body weight. That’s a lot of stress for your knees to bear!
All of that stress on the knees is cumulative. So, it’s not surprising that arthritis sets in later in life accumulated joint stress leads to gradual wearing away of the cartilage that cushions the bones with the knee joint. In extreme cases, the cartilage may erode to the point that the bones are completely exposed and rub against each other. At this point and sometimes earlier, knee pain and stiffness often set in. The changes associated with osteoarthritis of the knee is mostly degenerative, although some experts believe there’s also an inflammatory component.
The Role Exercise Plays in Keeping Knees Healthy
If osteoarthritis is due to wear and tear on the joint, you might wonder what impact exercise has on its development. Surprisingly, studies show that staying physically active is protective against osteoarthritis. People who are more physically active, in general, have a lower risk of developing symptomatic arthritis of the knees. But, what type of exercise is best?
As part of a study, researchers asked a group of older individuals with an average of 69 to take part in an exercise program. One group did 12 weeks of range-of-motion exercises using the lower body. The second group did lower body strength training exercises. The participants worked three times weekly for 12 weeks under supervision. At the end of a year, they switched to home-based workouts.
At the beginning of the study, during its course, and upon completion of the study, researchers monitored the status of the subjects’ knees with x-rays. The participants also underwent quadriceps strength testing. What they found was the individuals who strength trained had less age-related muscle loss relative to the group who did range-of-motion exercise. No surprise here! When you work your muscles against resistance, you reign in the loss of muscle strength and mass that goes along with aging.
What was more compelling is the impact strength training had on the progression of their knee osteoarthritis. Arthritis is marked by narrowing of the space between the two bones, that make up the joint. As osteoarthritis worsens, for example, in the knee, the joint space becomes narrower. Yet, they found that the group who strength trained reduced the rate of joint space narrowing by 26%. So, strength training is an ally in the battle against osteoarthritis, a problem that impacts a significant portion of the population.
Strength Training and Knee Osteoarthritis
Why might strength training help slow the progression of knee osteoarthritis? Experts believe that weak quadriceps are a contributing factor to knee osteoarthritis. By working the lower body against resistance, we strengthen the quads and potentially delay the onset and progression of osteoarthritis. Strong quad muscles help stabilize and protect the knee joint.
Fortunately, the focus is shifting with regard to knee arthritis. Previously, a doctor might have told a patient not to exercise and to strictly avoid high-impact exercise. But, today, evidence suggests that exercise helps with range-of-motion and knee function. In fact, a study found that exercise was as effective as non-steroidal anti-inflammatory medications for improving knee pain and function in people with knee osteoarthritis.
More often these days, practitioners prescribe a combination of low-impact exercise and lower extremity strength training for people with knee osteoarthritis. Exercise reduces pain and stiffness and helps lubricate the joints. Another form of exercise, Tai Chi, also shows benefits for knee osteoarthritis, according to some studies. Plus, Tai Chi lowers the risk of falls by improving balance skills.
Exercise, Obesity, and Knee Osteoarthritis
Another way exercise can help with knee osteoarthritis is by aiding in weight loss. Obesity is one of the strongest risk factors for knee osteoarthritis. Every extra pound a person carries on their frame magnifies the stress on the knees. Even modest amounts of weight loss lower the risk of developing knee osteoarthritis by reducing the force the knees are forced to bear.
Exercising to Prevent Osteoarthritis
Based on this study, one of the best things you can do to protect your knees is to strengthen your quadriceps muscles through strength training. What about aerobic exercise? It’s debatable as to whether high-impact exercise is harmful to the knee joints. If you’re at high risk of osteoarthritis, it’s best to do it in moderation, rather than running marathons every weekend, and wear shoes that reduce the impact on your knees when you run or jump. It’s also a good idea to cross train so your knees aren’t exposed to the same type of repetitive stress over and over again.
The Bottom Line
Movement is important for preventing arthritis of the knees and strength training plays a key role in keeping your knees healthy. So, keep moving, but make sure you’re cross-training, working with weights, and wearing the right shoes!
Internal Medicine News. “Strength Training May Stave Off Knee Osteoarthritis”
Up-to-Date.com. “Managing Knee Osteoarthritis”
Harvard Health Publishing. “Why weight matters when it comes to joint pain”
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