RELATED: What Does Arthritis Pain Feel Like? “Our study findings convey a reassuring message that adults at high risk for knee OA may safely engage in long-term strenuous physical activity at a moderate amount to improve their general health and well-being,” says lead author Alison Chang, an associate professor of physical therapy and human movement sciences at Northwestern Medicine in Chicago. “This research should be encouraging for people in the higher-risk group for knee osteoarthritis,” says David Fitz, MD, an orthopedic surgeon and assistant professor of orthopedics and sports medicine at UW Medicine in Seattle, who was not involved in the study. “If you’re a runner, a skier, a tennis player, this study says you can keep doing those things if they’re important to your life.”
Knee Osteoarthritis Risk Factors: Who Is Likely to Develop KOA?
Osteoarthritis (OA) is the most common kind of arthritis, affecting over 32.5 million people in the United States. People over 50 are at a higher risk for KOA, which happens when the cartilage within the joint and the bone underneath begins to change, causing pain and stiffness, according to the Centers for Disease Control and Prevention. It’s estimated that 38 to 45 percent of people develop KOA over their lifetime. In addition to age, such factors as carrying extra weight, a personal history of joint injury, a family history of arthritis, or systemic inflammation from diseases such as rheumatoid arthritis increase the chance that a person will develop osteoarthritis.
Does Sitting or Strenuous Activity Lead to an Increased Risk of Knee OA?
To find out how strenuous activity and sitting may impact the likelihood of developing KOA, investigators used data from the Osteoarthritis Initiative, a longitudinal observational study of 1,194 men and women between age 45 and 79 who were considered at risk of developing knee OA. These participants were considered high risk based on their age, body mass index (BMI), or history of knee injury or surgery, says Chang. “For instance, people suffering from knee injuries or [who’ve] had arthroscopic surgical repair of [the] anterior cruciate ligament or meniscus are often warned that they are well on the path to developing knee OA,” she says. That group is likely to want to continue vigorous activities, such as jogging, cycling, tennis, aerobic exercises, or skiing, but they are nervous about pain flares and further tissue damage, she adds. RELATED: 6 Smart Ways to Lose Weight if You Have Knee Osteoarthritis The level of strenuous physical activity and the amount of extensive sitting for each participant was determined by a combination of two methods. First, researchers asked participants to answer two questions about the number of days and hours they did strenuous physical activities, such as jogging, swimming, cycling, singles tennis, aerobic dance, and skiing in the last week. Second, they provided a questionnaire called a PASE (Physical Activity Scale for the Elderly), a short, self-administered test that asks participants to recall the amount of activity they did in the past seven days. Researchers asked participants about how long and how often they did sitting activities like reading, watching television, or doing crafts; extensive sitting was defined as sitting for four hours or longer for five or more days over the last seven days. Participants were divided into four groups based on their activity level, ranging from no strenuous activity to a high amount, and three subgroups based on how much time they spent sitting. Over the 10-year follow-up period, 13 percent of the study participants developed radiographic KOA as detected by an X-ray. After adjusting for factors such as age, BMI, and gender, researchers found that participating in highly strenuous activities was not associated with developing knee osteoarthritis. There was also no evidence of an association between extensive sitting and KOA. These findings are very relevant and good information to share, says Dr. Fitz. “I have a lot of patients come in and ask me, ‘Can I do any harm to my knee?’ For individuals who are in a little bit of pain or fall into one of these high-risk categories, this helps us advise the patient that they can continue to work out,” he says. “This study doesn’t exactly show that the activity has a protective benefit; the numbers trend toward significance but fall just short of that.”
People With Weak Knees or Genetic Predispositions May Need to Adjust Activity
“Arthritis is a multifactorial condition, which means there is a genetic component to it, but it’s not in the same way as your eye color or hair color. It takes both genetic and environmental factors to develop arthritis,” Fitz says. This study doesn’t investigate if the subjects had a family history of early arthritis or if they had a preexisting deformity, he says. “We do know from previous research that people who are knock-kneed or bowlegged put abnormal forces across their knees; it’s just the way their bodies were designed, so to speak.” People with those characteristics may want to consider doing low-impact strenuous activities instead, such as cycling, elliptical machines, or swimming, he says. “Doing low-impact activities can have multiple benefits, not only with weight loss and heart health. There can also be some upregulation of anti-inflammatory cytokines that can actually help the knee tamp down some of this osteoarthritic inflammation,” he says. RELATED: Restless Sleep and Knee Osteoarthritis: What You Need to Know
Movement Is Essential for Joint Health
“The 2018 Physical Activity Guidelines for Americans recommend at least 150 minutes per week of moderate-intensity activity or 75 minutes per week of vigorous-intensity activity, or an equivalent combination of both,” says Chang. If a person were to engage in 75 minutes of weekly vigorous aerobic activity, they would be less likely to develop knee OA, according to the findings, she notes. “Your joints are not like car tires that wear out as you use them. Movement and exercise are essential to joint health, because they help nourish the cartilage and aid in the removal of waste products,” says Chang. Activity can also stimulate and strengthen the bone and cartilage, and stronger muscles will help support the joint and absorb shock during impact, she adds. RELATED: 13 Natural Treatments for Osteoarthritis
Warning Signs That You May Be Pushing Your Knees Too Hard
Even though activity is good in relation to knee osteoarthritis, you don’t want to overdo it and damage your knees. There are a few signs that you need to back off your activity level, according to Chang.
A sudden increase in knee swellingSevere pain, such that you have trouble standing on one legAches and pains that are higher than 5 on a scale of 1 to 10 and last more than 24 hours after exercisingYour knee feeling unstable, as if it is shifting, or like it will give wayYour knee locking up during movement
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Expert Tips for Those at Risk for Knee Osteoarthritis
Exercise and physical activity are considered the frontline nondrug management for KOA, according to Chang. “It’s important to stay active, keep moving, and maintain a healthy body weight,” she says. RELATED: 10 Dos and Don’ts for Managing Knee Osteoarthritis Pain “If you have not been physically active, start slowly and incrementally increase activity intensity or amount each week. If you have already engaged in regular moderate to vigorous physical activity, make sure you alternate between high- and low-impact activities each day,” says Chang. “The big takeaway from this study is that movement is good, even in individuals with arthritis,” says Fitz. “It’s good for your overall body health and weight control, and helps keep the knees and hips from stiffening up.” Remember that strenuous activity doesn’t have to equal high-impact activity. There are ways to get a good workout that’s safe for joints if you have preexisting pain, he says. “There’s a big difference between swimming or cycling versus skiing down black diamond slopes,” says Fitz. It’s a good idea to check in with your doctor to make sure you’re doing the appropriate exercise for your knees and overall health, he adds.
