Poor Thigh Muscle Strength May Increase Women’s Risk of Knee OA
A study published in Arthritis Care & Research reports that women who have poor lower thigh muscle strength may be at increased risk for knee osteoarthritis (OA). Interestingly, the same is not true of men, the study found.
The relationship between poor thigh muscle strength and female gender was confounded by body mass index (BMI), which itself is known as a risk factor for knee OA.
For the study, the investigators measured isometric extensor and flexor muscle strength in 161 patients with radiographic signs of knee OA and 186 controls without knee OA. Both groups underwent MRI to determine the thigh muscle anatomic cross-sectional areas (ACSAs).
Specific strength was then calculated by dividing strength by ASCA (strength/ASCA). Women, but not men, with lower knee extensor and flexor specific strength scores were at greater risk for knee OA (OR 1.47 [95%CI 1.10, 1.96] for extensor strength and 1.41 [1.06, 1.89] for flexor strength).
The investigators noted that there may be more contractile tissue (and strength) present in men with greater BMI and more non-contractile (fat) tissue in women with greater BMI. The sex-specific relationship between muscle strength and BMI provides a possible explanation for why women with muscle strength deficits typically have a poorer prognosis than men with similar deficits.
“Our results highlight the importance of maintaining thigh muscle strength to reduce the risk of knee osteoarthritis development, particularly in women,” said Adam Culvenor, PT, PhD, the study’s lead author
“The different relationships we observed between muscle weakness, muscle size, BMI, and knee osteoarthritis development in men and women suggest that the mechanism by which BMI increases the risk of knee osteoarthritis is sex-specific and may require distinct treatment approaches.”
Culvenor AG, Felson DT, Niu J, et al. Thigh muscle specific strength and the risk of incident knee osteoarthritis: The influence of sex and greater body mass index. Arthritis Care & Research. Accepted Author Manuscript published online February 8, 2017. doi:10.1002/acr.23182