Voinier, Dana2022-03-292022-03-292021https://udspace.udel.edu/handle/19716/30722For years, knee osteoarthritis (OA) has been misunderstood as “wear and tear” of the knees. Minimizing “wear and tear” seems critical to adults with or at risk for knee OA; thus, many adults have become reluctant to increase their physical activity (PA). However, there is a global initiative to increase PA in all adults for general health benefits, as most adults do not meet the minimum recommended level of PA. Engaging in such a low level of PA should minimize “wear and tear” on the knees of these adults, yet the prevalence of knee OA is higher than ever. Further, researchers now accept that knee OA is not simply due to “wear and tear”, but there is highly mixed evidence as to whether PA can still increase risk for worsening knee OA. Thus, an important question remains: what role, if any, does PA have in knee OA? ☐ To address this question, we conducted epidemiologic studies using data from two large cohort studies of adults with or at risk for knee OA. We also performed a systematic search of available evidence related to this question, then synthesized their findings in the form of a narrative overview. ☐ In Aim 1, we found that adults who had a normal body mass index (BMI) and walked less than 6,000 steps/day had higher risk for worsening knee cartilage damage, compared with adults of a similar BMI but who walked between 6,000–19,500 steps/day. This finding provided preliminary evidence for potential underloading of the knee, which may explain why so many adults with a low level of PA still develop knee OA. ☐ In Aim 2, we found that adults who reported more than 4 hours/day of leisure-time sitting had higher risk for structural worsening of knee OA, compared with adults who reported less than 4 hours/day of leisure-time sitting. This finding provided additional evidence for underloading due to higher levels of sitting. ☐ In Aim 3, we found that higher time spent in moderate-to-vigorous intensity PA (MVPA) had no effect on structural worsening of knee OA, while also considering the effects of time spent in light intensity PA (LPA) or sedentary time (SED). To accomplish this aim, we used a novel approach to PA research called compositional data analysis (CoDA), which should be employed in future studies. ☐ Finally, in Aim 4, we found that there is consistent evidence that adults who meet or exceed the minimum recommended level of PA are not at higher risk for structural worsening of knee OA. Our narrative overview distilled available evidence into clear, concise recommendations for how clinicians can prescribe PA to adults with knee OA. ☐ Collectively, these findings advance our understanding of the role of PA in knee OA, and support future directions for research (e.g., underloading, CoDA) that were previously unexplored.CartilageKnee osteoarthritisMagnetic resonance imagingPhysical activityRadiographSittingThesis1306218798https://doi.org/10.58088/0m5k-e6302022-01-19en