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People at high risk for knee osteoarthritis (OA) may be reluctant to participate in strenuous physical activities such as jogging, cycling, singles tennis, and skiing. But a new study from Northwestern Medicine, published in JAMA Network Open, suggests that fear may be unfounded: A cohort of high-risk individuals who engaged in vigorous exercise did not experience an increase in their risk of developing OA. In fact, the exercise may have protected them from developing OA.

“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 level to improve their general health and well-being,” said Alison Chang, PT, DPT, MS, associate professor of physical therapy and human movement sciences at Northwestern University Feinberg School of Medicine.

Osteoarthritis is the most common joint disorder in the United States, affecting an estimated 32.5 million adults, according to the Centers for Disease Control and Prevention. The knee is the most commonly affected joint. The lifetime risk of developing symptomatic, radiographic knee OA is approximately 38% to 45%, with an estimated median age at diagnosis of 55 years.

In this observational study of 1194 individuals at high risk for but without radiographic evidence of knee OA, long-term participation in strenuous physical activities was not associated with risk of developing radiographic knee OA. The vigorously exercising individuals in the study, who were followed for up to 10 years, were 30% less likely to develop OA, although the number was not considered statistically significant. The activities individuals participated in included jogging, swimming, cycling, singles tennis, aerobic dance and skiing.

Excessive body weight, history of joint injury or surgery, aging and chronic knee symptoms place an individual at elevated risk for developing knee OA. Although regular physical activity and exercise provide multiple health benefits, uncertainty about whether vigorous physical activity participation could cause pain and further tissue damage is a common concern. The researchers’ analysis showed nearly 50% of the adults at high risk for this disease did not engage in any strenuous physical activity over 8 years.

“People suffering from knee injuries or who had arthroscopic surgical repair of ACL or meniscus are often warned that they are well on the path to develop knee OA,” Dr. Chang said. “They may be concerned that participating in vigorous activities or exercises could cause pain and further tissue damage. To mitigate this perceived risk, some have cut down or discontinue strenuous physical activities, although these activities are beneficial to physical and mental health.”

The study analyzed data from the Osteoarthritis Initiative, a longitudinal observational study of men and women (age range 45 to 79 years) with or at an increased risk of developing knee OA, recruited from 4 communities in the U.S. At the study onset and at subsequent visits for up to 10 years of follow-up, radiographs were obtained of both knees to determine knee OA disease status. Participants also reported their weekly strenuous physical activity participation and sitting patterns.

Among the 1194 participants, researchers identified 4 distinct long-term trajectory patterns of strenuous physical activity participation and 3 distinct trajectory patterns of extensive sitting over an 8-year period.

Physical Activity

• Persistently no (n=594)
• Low, slightly improving (n=354)
• Moderate, declining (n=151)
• High, improving (n=95)

Sitting

• High frequency (n=121)
• Moderate frequency (n=386)
• Low frequency (n=687)

The researchers then examined the data to determine if long-term engagement of strenuous physical activity or extensive sitting behavior were associated with risk of developing knee OA. Radiographs from the follow-up period showed knee OA in all subgroups: 15.3%, (persistently no), 10.7% (low, slightly improving), 9.3% (moderate, declining), and 12.6% (high, improving) in the physical activity subgroups, and 14.0% (high frequency), 13.7% (moderate frequency), and 12.4% (low frequency) in the sitting subgroups. But after adjusting for age, sex, and BMI, the researchers found no association between strenuous physical activities and development of knee OA or between extensive sitting and knee OA.

“Adults at high risk for knee OA may safely engage in long-term strenuous physical activity at a moderate level,” Dr. Chang said. “Health care providers may consider incorporating physical activity counseling as part of the standard care for high-risk individuals at an early stage when physical activity engagement is more attainable.”

Source

Chang AH, Lee JJ, Chmiel JS, Almagor O, Song J, Sharma L. Association of long-term strenuous physical activity and extensive sitting with incident radiographic knee osteoarthritis. JAMA Netw Open. 2020 May 1;3(5):e204049. doi: 10.1001/jamanetworkopen.2020.4049.