Arthritis care & research;
Objective: Quadriceps weakness, associated with functional limitations, is a target of treatment of knee osteoarthritis (OA). Limited data exist on modest strength increases and improvements in function. We evaluated concurrent change in strength and physical function over 5 years. Methods: Using subjects from the Multicenter Osteoarthritis (MOST) study, we excluded those with knee replacement after baseline. A 3-category variable defined whether, at 5 years, knee extensor strength increased, decreased or remained within 15% of baseline, a clinically important cutoff. Outcomes: Five-Times Sit-to-Stand-Test, 20-Meter Walk Test, WOMAC Physical Function Score, and 3 individual physical functions from WOMAC: arising from a chair, going up stairs and getting on/off toilet. Linear and logistic models, stratified by sex, evaluated associations between change in strength and change in physical function over 5 years. To compare weaker vs. stronger women, we stratified analyses at 56Nm baseline strength. Results: Among 1534 participants (60.6% women), 22% of men and 30% of women increased strength by at least 15% at 5 years. Compared with women whose strength did not change, women whose strength increased had improved chair stand performance (OR=2.27, 95% CI 1.56, 3.30) but no improvements in other functions. In men, increase in strength was not associated with significant improvement in physical function. 20% or 30% change showed similar results. Conclusion: Modest improvement in quadriceps strength was associated with improved chair stand performance in women, but not in men. Most functions did not improve with an increase in strength, and may require targeted interventions to improve functional status.
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