Background

To date, there have not been any epidemiologic studies that have evaluated the association between swimming over a lifetime and knee health.

Objective

The study aimed to evaluate the relationship of a history of swimming with knee pain, radiographic knee OA (ROA), and symptomatic knee OA (SOA).

Design

Cross-sectional retrospective study.

Setting

Four academic centers in the United States.

Participants

Respondents to the historical physical activity survey within the Osteoarthritis Initiative with knee radiographs and symptom assessments.

Methods

In this retrospective study nested within the Osteoarthritis Initiative, researchers performed logistic regression with the predictor being swimming over a lifetime and over particular age ranges.

Main outcome measurements

Person-based definitions of frequent knee pain, ROA, and SOA.

Results

A total of 2637 participants were included, with a mean age of 64.3 years (SD 8.9), body mass index of 28.4 kg/m² (SD 4.9), and 44.2% male. Over a lifetime, the adjusted prevalence measures for frequent knee pain, ROA, and SOA for any versus no history of swimming were 36.4% (33.4% - 39.5%) v. 39.9% (37.4% - 42.5%), 54.3% (51.0% - 57.6%) v. 61.1% (58.4% - 63.7%), and 21.9% (19.4% - 24.7%) v. 27.0% (24.7% - 29.4%) respectively.

Conclusions

This is the first epidemiologic study to indicate that swimming is potentially beneficial toward knee health, particularly when performed earlier in life (before age 35). Future prospective studies are needed to confirm these findings and to better scrutinize the associations in older age groups.

Objective

Regular physical activity, including running, is recommended based on known cardiovascular and mortality benefits. However, controversy exists regarding whether running can be harmful to knees. The purpose of this study is to evaluate the relationship of running with knee pain, radiographic osteoarthritis (OA), and symptomatic OA.

Methods

This was a retrospective cross-sectional study of Osteoarthritis Initiative participants (2004-2014) with knee radiograph readings, symptom assessments, and completed lifetime physical activity surveys. Using logistic regression, we evaluated the association of history of leisure running with the outcomes of frequent knee pain, radiographic OA, and symptomatic OA. Symptomatic OA required at least 1 knee with both radiographic OA and pain.

Results

Of 2,637 participants, 55.8% were female, the mean ± SD age was 64.3 ± 8.9 years, and the mean ± SD body mass index was 28.5 ± 4.9 kg/m² ; 29.5% of these participants ran at some time in their lives. Unadjusted odds ratios of pain, radiographic OA, and symptomatic OA for those prior runners and current runners compared to those who never ran were 0.83 and 0.71 (P for trend = 0.002), 0.83 and 0.78 (P for trend = 0.01), and 0.81 and 0.64 (P for trend = 0.0006), respectively. Adjusted models were similar, except radiographic OA results were attenuated.

Conclusion

There is no increased risk of symptomatic knee OA among self-selected runners compared with nonrunners in a cohort recruited from the community. In those without OA, running does not appear to be detrimental to the knees.

Higher levels of moderate to vigorous physical activity improve all-cause mortality and cardiovascular events. However, the effect of running, a moderate to vigorous activity, in those with knee osteoarthritis (OA), a common arthritis that occurs with aging, a high-risk group for mortality and cardiovascular events, is unclear. Therefore, we aimed to evaluate the association of self-selected running on OA symptom and structure progression in people with knee OA. This nested cohort study within the Osteoarthritis Initiative (OAI) (2004-2014) included those at least 50 years old with OA in at least one knee. Runners were defined using a self-administered questionnaire at the 96-month visit. At baseline and 48-months, symptoms were assessed and radiographs were scored for Kellgren-Lawrence (KL) grade (2-4) and medial Joint Space Narrowing (JSN) score (0-3). We evaluated the association of self-selected running with outcomes: KL worsening, medial JSN worsening, new knee pain, and improved knee pain over 48 months, adjusting for baseline age, sex, body mass index (BMI), KL score, contralateral KL score, contralateral knee pain, and injury. If data were not available at the 48-month visit, then they were imputed from the 36-month visit. One thousand two hundred three participants had a mean age of 63.2 (7.9) years, BMI of 29.5 (4.6) kg/m2, 45.3% male, and 11.5% runners. Data from 8% of participants required imputation. Adjusted odds ratios for KL grade worsening and new frequent knee pain were 0.9 (0.6-1.3) and 0.9 (0.6-1.6) respectively. Adjusted odds ratio for frequent knee pain resolution was 1.7 (1.0-2.8). Among individuals 50 years old and older with knee OA, self-selected running is associated with improved knee pain and not with worsening knee pain or radiographically defined structural progression. Therefore, self-selected running, which is likely influenced by knee symptoms and may result in lower intensity and shorter duration sessions of exercise, need not be discouraged in people with knee OA.