Strenuous Physical Activity May Be Beneficial—Not Harmful—for Patients At Risk of Knee Osteoarthritis

Contrary to a commonly held belief, patients who are at a high risk of developing osteoarthritis (OA) of the knee who engage in strenuous physical activity are not increasing these odds but may in fact be lowering them, according to a study.

“Persons with knee symptoms recognize the health benefits of engaging in physical activity, but uncertainty persists about whether regular strenuous physical activity or exercise can accelerate tissue damage. A sedentary lifestyle of inactivity or underloading may also be associated with deleterious joint health,” the study authors explained. They therefore sought to determine the risk of knee OA associated with two opposites behaviors: long-term strenuous physical activity participation and extensive sitting.

The study assessed data from the Osteoarthritis Initiative, which studies men and women with or a with a greater risk of developing symptomatic, radiographic knee OA. Adults from four sites were recruited and followed for 10 years. Eligible patients had a baseline Kellgren and Lawrence grade 0 in both knees, and filled out a Physical Activity Scale for the Elderly (PASE) questionnaire at baseline and at least two more times during follow-up over an eight-year period. The exposure was baseline to eight-year trajectories of participating in strenuous physical activity and extensive sitting, identified with group-based trajectory models. The primary outcome was incident radiographic knee OA, defined as a Kellgren and Lawrence grade 2 or higher in either knee at final follow-up.

Strenuous Activity Not Correlated with Greater Knee OA Risk

Final analysis included 1,194 patients (58.4% were female) with a mean age of 58.4 years and mean body mass index (BMI) of 26.8 kg/m2 at baseline. The researchers identified four distinct trajectories of weekly hours spent in strenuous physical activities and three distinct trajectories of extensive sitting. The risk of 10-year incident radiographic knee OA was not increased by long-term engagement in low-to-moderate physical activities (adjusted odds ratio [OR]=0.69; 95% confidence interval [CI], 0.48 to 1.01) or any strenuous physical activities (adjusted OR=0.75; 95% CI, 0.53 to 1.07); persistent extended sitting was not correlated with knee OA. While patients had mild symptoms and were high function, nearly half (49.7%) participated in no strenuous physical activities (zero hours/week) over eight years; 42.5% took part in persistent moderate-to-high frequency of extensive sitting. The following factors were predictive of persistent lack of engagement in strenuous physical activities: older age, higher BMI, more severe knee pain, non-college graduate educational level, weaker quadriceps, and depression.

The results were published in JAMA Network Open.

“People suffering from knee injuries or who had arthroscopic surgical repair of [anterior cruciate ligament] or meniscus are often warned that they are well on the path to develop knee OA,” said Alison Chang, MD, associate professor of physical therapy and human movement sciences at Northwestern University Feinberg School of Medicine, in a press release. “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.”

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