Weight-Bearing Physical Activity, Lower-Limb Muscle Mass, and Risk of Knee Osteoarthritis

Abstract

Importance: It has been demonstrated that total physical activity is not associated with risk of osteoarthritis. However, the association of different types of physical activity with incident knee osteoarthritis remains unclear.

Objective: To determine whether weight-bearing recreational physical activities are associated with increased risk of incident knee osteoarthritis.

Design, setting, and participants: This prospective cohort study used data from the Rotterdam Study (1996 to 2009), including participants with knee x-ray measurements at baseline and follow-up examinations. Participants with knee osteoarthritis at baseline were excluded. Residents aged 45 years and older of the Ommoord district in the city of Rotterdam in The Netherlands were invited to join the Rotterdam Study (78% response rate). Analysis was conducted in June 2023.

Exposure: Total, weight-bearing, and non-weight-bearing recreational physical activities collected by questionnaires at baseline.

Main outcomes and measures: Incident radiographic knee osteoarthritis measured by knee x-ray was the primary outcome, and incident symptomatic knee osteoarthritis defined by x-ray and knee pain questionnaire was the secondary outcome. The association of different types of recreational physical activity with radiographic knee osteoarthritis was examined using logistic regression within generalized estimating equation framework after adjusting for potential confounders. A prespecified stratification analysis was planned on the basis of lower-limb muscle mass index (LMI) tertiles, measured by dual-energy x-ray absorptiometry.

Results: A total of 5003 individuals (2804 women [56.0%]; mean [SD] age, 64.5 [7.9] years) were included. The knee osteoarthritis incident rate was 8.4% (793 of 9483 knees) for a mean (SD) follow-up time of 6.33 (2.46) years. Higher weight-bearing activity was associated with increased odds of incident knee osteoarthritis (odds ratio [OR], 1.22; 95% CI, 1.10-1.35; P < .001), but non-weight-bearing activity was not (OR, 1.04; 95% CI, 0.95-1.15; P = .37). In the analysis stratified by LMI tertiles, the association of weight-bearing activity with incident osteoarthritis was found only among 431 patients in the lowest LMI tertile (OR, 1.53; 95% CI, 1.15-2.04; P = .003), but not among patients in the middle or high LMI tertile.

Conclusions and relevance: The findings of this study suggest that weight-bearing activity is associated with incident knee osteoarthritis in people with low levels of lower-limb muscle mass, which might be a promising avenue for tailored advice for physical activity.

Figure 1.. Design of the Rotterdam Study (RS)

RS-I-3 and RS-I-4 refer to re-examinations of the original cohort members. RS-II-1 refers to the extension of the cohort with persons from the study district who had turned 55 years old since the start of the study or those aged 55 years or older who migrated into the study district. RS-II-2 and RS-II-3 refer to re-examinations of the extension cohort. RS-III-1 refers to another extension of the cohort with persons aged 45 years and older living in the study district who had not been examined already (ie, mainly comprising those aged 45-60 years). RS-III-2 refers to the first re-examination of this third cohort.

Figure 2.. Flowchart for Individuals Included for Analysis

Chart shows overview of the Rotterdam Study (RS) population and performed analysis. Radiographic knee osteoarthritis (OA) incidence was defined as baseline knee Kellgren and Lawrence grade of 1 or lower and 2 or higher at follow-up or having a total knee replacement at follow-up. Symptomatic OA incidence was defined as baseline knee Kellgren and Lawrence grade 1 or lower with negative knee pain, combined with Kellgren and Lawrence grade 2 or higher, or having a total knee replacement at follow-up with positive knee pain.

Figure 3.. Association of Recreational Physical Activity and Osteoarthritis Stratified by Lower Limb Muscle Index (LMI) Tertiles

The statistical model used is a generalized estimating equation multivariate logistic regression model. Results are from the model adjusted for age, sex, Rotterdam Study subcohorts, body mass index, follow-up time, and baseline Kellgren and Lawrence grade. OR indicates odds ratio. ^aIndicates that P value remained significant after multiple testing corrections using Benjamini and Hochberg method.