Relationship Between Isometric Thigh Muscle Strength and Minimum Clinically Important Differences in Knee Function in Osteoarthritis: Data From the Osteoarthritis Initiative

Abstract

Objective To determine the relationship between thigh muscle strength and clinically relevant differences in self-assessed lower limb function. Methods Isometric knee extensor and flexor strength of 4553 Osteoarthritis Initiative participants (2651 women/1902 men) was related to Western Ontario McMasters Universities (WOMAC) physical function scores by linear regression. Further, groups of Male and female participant strata with minimal clinically important differences (MCIDs) in WOMAC function scores (6/68) were compared across the full range of observed values, and to participants without functional deficits (WOMAC=0). The effect of WOMAC knee pain and body mass index on the above relationships was explored using stepwise regression. Results Per regression equations, a 3.7% reduction in extensor and a 4.0% reduction in flexor strength were associated with an MCID in WOMAC function in women, and a 3.6%/4.8% reduction in men. For strength divided by body weight, reductions were 5.2%/6.7% in women and 5.8%/6.7% in men. Comparing MCID strata across the full observed range of WOMAC function confirmed the above estimates and did not suggest non-linear relationships across the spectrum of observed values. WOMAC pain correlated strongly with WOMAC function, but extensor (and flexor) muscle strength contributed significant independent information. Conclusion Reductions of approximately 4% in isometric muscle strength and of 6% in strength/weight were related to a clinically relevant difference in WOMAC functional disability. Longitudinal studies will need to confirm these relationships within persons. Muscle extensor (and flexor) strength (per body weight) provided significant independent information in addition to pain in explaining variability in lower limb function.

Reliability of a device for the knee and ankle isometric and isokinetic strength testing in older adults

“…In the first study, the relationship between thigh muscle strength and clinically relevant differences in self-assessed lower limb function was estimated, while in the second investigation testretest reliability of lower limb isokinetic endurance in COPD patients was taken in examination. Averagely, both studies described a threshold of about 6% 29 and 10% 30 respectively to determine a minimally clinical relevant change. It has to be considered that our data reflected a performance in a healthy population; however, the magnitude of error in the system showed a range concretely inferior to the minimal clinically relevant differences detected in these investigations.…”

“…From a clinical standpoint, as comparison with our data, we extract data from Ruhdorfer et al 29 and Ribeiro et al 30 . In the first study, the relationship between thigh muscle strength and clinically relevant differences in self-assessed lower limb function was estimated, while in the second investigation testretest reliability of lower limb isokinetic endurance in COPD patients was taken in examination.…”

Which Predicts Quadriceps Muscle Strength in Knee Osteoarthritis: Biological Markers or Clinical Variables?

“…On the other hand, in consistence with our study, several studies so far have demonstrated the correlation between quadriceps strength and functionality. 19,20 The results of these studies indicated that decreased isometric quadriceps muscle strength is related to knee symptoms and WOMAC functional disability. 19,20 25-hydroxy vitamin D levels were not correlated with quadriceps muscle strength and patients' functional status in the current study.…”

“…19,20 The results of these studies indicated that decreased isometric quadriceps muscle strength is related to knee symptoms and WOMAC functional disability. 19,20 25-hydroxy vitamin D levels were not correlated with quadriceps muscle strength and patients' functional status in the current study. Similarly, Al-Jarallah et al 21 did not find any relationship between 25-(OH)D and the functional status of patients with primary knee OA in their crosssectional study.…”

Determining the minimally important difference in quadriceps strength in individuals with COPD using a fixed dynamometer

“…The MID is a useful expression defined as “the minimal amount of change required between two points in time to be confident that a patient has truly changed” 23. A reduction of 4% in isometric force has been suggested as the minimal change to bring about a relevant difference in osteoarthritis of the knee 24. Similarly, a preliminary result by Quessada et al suggested an MID of 33 Nm for QMVC in individuals with COPD undergoing exercise training 25.…”