<p>Declining knee extensor strength (KES) is a recognized risk factor for musculoskeletal disorders including knee osteoarthritis. Regular self-assessment of knee extensor strength in older women is essential for prevention of the progression. This study aimed to clarify the relationship between the KES and parameters derived from shoe-based wearable sensors during natural walking. Thirty-seven older women participated in this study. Insole force sensors and shoe-mounted IMU sensors were used to obtain spatiotemporal, ground reaction force (GRF), and foot pitch angle parameters. The maximal isometric KES was measured, and simple and partial correlations (controlling for gait speed and age) were calculated. KES was significantly correlated with (1) percentages of the stance and double-stance phases (<i>r</i> = -0.58 to -0.46), (2) timing of the first peak of the vertical GRF (<i>r</i> = -0.57), and (3) foot pitch angle at toe-off (<i>r</i> = -0.56). Furthermore, these parameters remained significantly associated with the KES after controlling for gait speed and age. These findings may contribute to the development of wearable sensor–based systems to estimate and quantify knee extensor strength using daily walking data.</p>