Cohort study finds benefit of 1-2 hours/week

When knee pain flares in older adults, it may trigger a response of either stopping their strenuous physical activity or quitting exercise all together in fear that knee osteoarthritis (KOA) is in their future.

However, neither is a good option, and, in fact, staying with their active routine might be beneficial and protective against developing KOA, according to a new cohort analysis.

“In persons at high risk but without radiographic evidence of KOA, engaging in long-term strenuous physical activity (e.g., jogging, swimming, cycling, singles tennis, aerobic dance, and skiing) over an 8-year period was not associated with risk of incident radiographic KOA,” Alison H. Chang, PT, DPT, MS, from the Department of Physical Therapy and Human Movement Sciences, Northwestern University Feinberg School of Medicine, Chicago, and colleagues reported in JAMA Network Open. “The adjusted ORs ranged from 0.69 (95%CI, 0.48-1.01) for low-to-moderate level of strenuous physical activities to 0.75 (95% CI 0.53-1.07) for any strenuous physical activities, suggesting that, even in persons at high risk for KOA, strenuous physical activity is not associated with development of radiographic changes.”

Chang and colleagues noted that their findings support a strategy of strenuous physical activity for 1-2 hours a week as a means of joint protection. “We believe that these results also convey a reassuring message that older adults at high risk for KOA for whom regular physical activity provides multiple health benefits may safely engage in long-term strenuous physical activity at a moderate level,” the study authors wrote.

Kicking back and taking to a more sedentary lifestyle with knee pain neither elevated nor reduced the risk of incident radiographic KOA.

Chang and colleagues looked at data from the Osteoarthritis Initiative (OAI), a prospective longitudinal cohort study of men and women who are considered with or at increased risk of developing symptomatic, radiographic KOA. The participants were 45-79 at enrollment, which began in 2004 and took place at four study sites in the U.S. The individuals were followed up for 10 years.

“Individuals were included if they had a baseline Kellgren and Lawrence grade of 0 in both knees and completed a PASE (Physical Activity Scale for the Elderly) questionnaire at baseline and at least 2 follow-up visits over an 8-year interval,” the study authors reported. They conducted their analyses from May-Nov. 2018.

Based on the PASE scale, the study authors estimated how many hours per week over an 8-year-period the participants engaged in strenuous physical activity such as jogging, swimming, cycling, aerobic dance, etc.

“Weekly hours of engagement in strenuous physical activities were estimated by combining the midpoint quantity of the frequency and duration responses from the PASE questionnaire. For example, a response of ’3-4 days/week’ and ’1 to <2 hours/day’ was estimated as 3.5 days per week and 1.5 hours per day, which produced weekly hours of 5.25,” the authors explained.

Their study sample included 1,104 participants; more than half, 667, were women, the mean (SD) age was 58.4 (8.9), and their mean BMI was 26.8.

Four distinct trajectories of weekly strenuous physical activity were identified — “Persistently no” (n=594), “low, slightly improving” (n=354), “moderate, declining” (n=151), and “high, improving” (n=95). And, there were three distinct sitting trajectories — low frequency (n=687), moderate frequency (n=386), and high frequency (n=121).

Chang and colleagues found that, of all the participants, 13% (155) developed radiographic KOA by the 10-year follow-up visits.

“The respective radiographic KOA incidence rates for the 4 strenuous physical activities trajectory subgroups were 15.3% (persistently no), 10.7% (low, slightly improving), 9.3% (moderate, declining), and 12.6% (high, improving),” the study authors wrote. “For the 3 extensive sitting trajectory subgroups, the incidence rates were 14.0% (high frequency), 13.7% (moderate frequency), and 12.4% (low frequency).

“Compared with persistently no strenuous physical activities, participating in any (unadjusted OR, 0.66; 95% CI, 0.47-0.93) and in low-to-moderate level strenuous physical activities (unadjusted OR, 0.64; 95% CI, 0.44-0.91) over 8 years were each associated with a reduced likelihood of incident radiographic KOA over the baseline to 10-year follow-up period,” they added.

Of note is that nearly half, or 594, of the study participants who had mild symptoms and high function did not engage in any strenuous physical activities during the 8-year-study period, while 507 (42.5%) were more engaged in moderate-to-high frequency of extensive sitting.

They also found that participants who were older, had a higher BMI, had more severe knee pain, were not college graduates, had weaker quadriceps, and had depression were associated with less physical activity.

“Exercise and physical activity are recommended as first-line management for KOA,” Chang and colleagues wrote. “Limited efficacy of current management may in part be attributable to its implementation at a later disease stage, when structural damage already exists and chronic pain sensitization may have occurred… Our findings suggest that targeting modifiable factors, including BMI, knee pain, depression, and quadriceps strength, may increase long-term any physical activity participation. In addition, physical activity promotion and sedentary reduction efforts may incorporate tailored approaches to engage those who are likely to be persistently inactive because of age, comorbidities, or educational level.”

Limitations of the study included the use of self-reporting to assess physical activity and sedentary behavior and, while the findings are generalizable to populations similar to the cohort studied, they cannot be generalized to other populations.

  1. In persons at high risk but without radiographic evidence of KOA, engaging in long-term strenuous physical activity (e.g., jogging, swimming, cycling, singles tennis, aerobic dance, and skiing) over an 8-year period was not associated with risk of incident radiographic KOA.

  2. Strenuous physical activity for 1-2 hours a week may confer joint protection and the study authors point out this is an area of opportunity for early intervention.

Candace Hoffmann, Managing Editor, BreakingMED™

The study was funded in part by grants from NIAMS/NIH.

Chang reported no conflicts of interest.

Cat ID: 438

Topic ID: 437,438,393,438,730,192,922,925