Comparison of knee muscle morphology, physical performance, and falls in middle- and old-aged adults with and without knee osteoarthritis

The purpose of this study was to investigate knee muscle morphological characteristic, physical performance, and fall incidence in middle- and old-aged adults with and without knee OA.

This cross-sectional study included 50 participants with knee OA (mean age 56.7 ± 7.9 years, Kellgren-Lawrence grading scale 0-3) and 51 healthy controls (mean age 55.9 ± 8.8 years). Key measures included muscle morphology (thigh muscle thickness via B-mode ultrasonography), sarcopenia criteria, and physical performance (maximal isometric knee extension and flexion torque, Five Times Sit to Stand Test [FTST], Timed Up and Go Test [TUG]). The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) was used to assess OA-related symptoms, and fall incidence was recorded.

Participants with knee OA demonstrated significantly lower skeletal muscle mass index and knee muscle thickness compared to healthy controls (p0.05). Physical performance measures, including maximal knee extension torque, FTST, TUG, and grip strength, were significantly poorer in the OA group compared to controls (p0.05). Despite these differences in muscle morphology and physical performance, there was no statistically significant difference in the incidence of falls between the OA and control groups. 

Knee extensor muscle size and strength are crucial to physical performance and balance in middle- and old-aged adults with knee OA. These deficits may increase the risk of sarcopenia, even in those with mild to moderate OA. Although sarcopenia was not overtly observed in the OA group, the reduction in muscle function highlights the need for interventions targeting muscle preservation to prevent future functional decline and fall risk. However, compensatory movement during walking should be considered with its performance. 

• Early intervention for falls prevention: Although sarcopenia was not explicitly observed in this study due to walking speed criteria, the reduced muscle size and function in the mild-to-moderate knee OA group suggest a precursor to sarcopenia and further functional decline. Early interventions aimed at preserving limb muscle mass and strength through resistance and functional exercises in middle- and old-aged adults with knee OA may prevent sarcopenia, improve balance, and reduce future fall risk.
• Assessment tools: The findings highlight impairments in muscle size, strength (particularly knee extensors), and functional balance in adults with mild-to-moderate nee OA. These indicators can serve as valuable tools for identifying fall risk factors and guiding rehabilitation programs to mitigate fall risks in middle- to old-aged adults with early stage of knee OA.