Low lower-limb muscle mass index with weight-bearing activity increases incidence of osteoarthritis

1. Increased incidence of radiographic knee osteoarthritis was associated with high amounts of weight-bearing activity only in those with a low lower-limb muscle mass index (LMI).

2. There was no association identified between symptomatic knee osteoarthritis and weight-bearing activity, total physical activity, or non-weight-bearing activity. 

Evidence Rating Level: 1 (Excellent) 

Osteoarthritis is an inflammatory joint disease involving the degeneration of joints along with chronic pain and limited mobility. These additive effects combined with the high prevalence lead to a burden on the health care system and a high socioeconomic cost. It is essential to identify modifiable risk factors in patients with osteoarthritis and to create and implement new prevention strategies. To assess the association between weight-bearing versus non-weight-bearing activities on incident knee osteoarthritis, this study was embedded in the Rotterdam Study (RS), a prospective cohort. From the RS, three subcohorts (RS-I, RS-II, and RS-III) with data for baseline physical activity, baseline knee pain, and baseline knee radiographs along with 1 additional follow-up radiograph, were analyzed. The Zutphen Physical Activity Questionnaire was adapted and used alongside the Longitudinal Aging Study Amsterdam questionnaire, to collect data for weight-bearing, and non-weight-bearing physical activity. X-ray knee osteoarthritis was assessed as the primary outcome, while symptomatic knee osteoarthritis was the secondary outcome. A total of 5003 individuals (2804 women [56.0%]; mean [SD] age, 64.5 [7.9] years) were included in the study as they had complete data. Over a mean (SD) follow-up time of 6.33 (2.46) years, there was an 8.4% (793 of 9483 knees) incident rate of knee osteoarthritis. Weight-bearing activity was associated with osteoarthritis found on x-ray (odds ratio [OR], 1.22; 95% CI, 1.10-1.35; P<.001) whereas non-weight-bearing activity had no association with new cases of radiographic osteoarthritis (OR. 1.04; 95% CI, 0.95-1.15; P=.37). The groups were also stratified based on lower-limb muscle mass index (LMI) which was assessed using a DXA scan. Weight-bearing activity and incident knee osteoarthritis (as seen on an x-ray) had a significant association among 431 participants in the lowest LMI tertile that did not have baseline knee pain (model 1, OR, 1.53; 95% CI, 1.15-2.04; P=.003).  Overall, increased weight-bearing activity was associated with an increased incidence of radiographic knee osteoarthritis in the low LMI subgroup.

Click to read the study in JAMA Network Open

Image: PD

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