Quadriceps Strength and Osteoarthritis Progression in Malaligned and Lax Knees

IN RESPONSE:

To Dr. Judge, we respond that we too are concerned about errors in the description of our findings and their implications. Our study dealt with the relationship between strength and progression in osteoarthritic knees that were also malaligned or lax. Strength had no deleterious effect in more neutral or stable knees. Also, we stated that these results have no implications for aerobic exercise or physical activity in general. It was important to report our results, regardless of whether they match what has been believed (in the absence of data) about the effect of strength on disease progression in knee osteoarthritis. Descriptive data for quadriceps strength in the sample were provided. Strength cutoffs in healthy persons and persons with osteoarthritis have not been established. Our results were not altered by separately adjusting for body mass (that is, weight) and height rather than BMI. In response to the comments of Dr. Moore, we point out that, as stated in the final paragraph of our Results section, strength was measured at baseline and at 18 months, and minimal change occurred. Further analyses revealed that the mean change in strength (a slight increase) did not differ between stronger and weaker participants; that the proportion of participants who lost strength was similar in stronger and weaker participants (for example, for 10% loss, the proportions were 20% and 19%, respectively); and that among those who declined in strength, the magnitude of decline did not differ between stronger and weaker participants. The results presented in our paper were adjusted for average physical activity. In theory, in some individuals, physical activity in the past may have contributed to disease development; the results presented in the paper are also adjusted for baseline disease severity.