Background/Purpose: Activity restriction (i.e. limiting or avoiding normal activity) is a common strategy to reduce, and sometimes eliminate, knee symptoms. Knee symptoms, such as pain, aching, or stiffness, may be indicative of knee osteoarthritis (OA), thus are a common reason that individuals seek health care services. One concern is that activity restriction may indicate in deteriorating function and development of OA, even if the knee remains symptom free. It is unclear how activity restriction is associated with physical function and knee OA, in the presence or absence of knee symptoms. The purpose of this analysis was to examine the associations of pain and activity restriction with physical function and OA in adults with or at risk for knee OA.

Methods: We conducted a cross-sectional analysis using baseline data from the Osteoarthritis Initiative, a cohort study of individuals with or at risk for knee OA. We defined people using activity restriction to manage knee symptoms as those who reported that they “avoid/reduce pain, aching, or stiffness by changing or cutting back on normal activities” in the past 30 days. We defined people with knee symptoms as people reporting “knee pain, aching, or stiffness on more than half of the past 30 days”. We created a four-category exposure by combining the answers to activity restriction (yes/no) and knee symptoms (yes/no). The outcomes of interest were physical function and radiographic knee OA (ROA). Physical function was assessed with the Short Form 12 Physical Component Score (SF-12 PCS), Western Ontario and McMaster Universities Osteoarthritis Index for function (WOMAC-function), and gait speed (m/s) from the 20-m walk test. ROA was defined as Kellgren-Lawrence grade ≥ 2 in either limb.  To examine the association of the exposure groups with physical function, we used a general linear model to calculate effect estimates with 95% confidence intervals (95% CI), adjusting for potential confounders. To examine the association of the exposure groups with ROA, we used binomial logistic regression to calculate odds ratios with 95% CI, adjusting for potential confounders.

Results: Of the full sample (N=4796, 58% women, 61±9 years old, 28.6±4.8 kg/m²), 45% reported neither activity restriction nor knee symptoms, 12% reported activity restriction only, 17% reported knee symptoms only, and 25% reported both activity restriction and knee symptoms. Compared to people reporting no activity restriction or knee symptoms, those who reported activity restriction and/or knee symptoms had worse self-reported and performance-based physical function (Table 1). Similarly, those reporting activity restriction and/or knee symptoms had higher odds of more (unilateral or bilateral) ROA compared to those reporting no activity restriction or knee symptoms (Table 2).

Conclusion: Individuals who restrict normal activities to avoid knee symptoms, or have knee symptoms, have worse physical function and higher prevalence of ROA compared to those who have neither. Identifying people who restrict normal activities to avoid pain may be a marker of early symptomatic progression.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/restricting-activity-to-evade-knee-symptoms-is-associated-with-worse-physical-function-and-radiographic-osteoarthritis/