The aim of this study was to evaluate the relationships among aging, muscle strength, and image feature analysis of the quadriceps femoris muscle and to evaluate the relationship between aging, muscle strength, and sonographic findings. One hundred forty-five healthy volunteers participated in the study. The participants were classified into 6 groups on the basis of sex and age. To assess muscle quality, texture analysis was defined with the following parameters: mean, skewness, kurtosis, inverse difference moment, sum of entropy, and angular second moment. The knee extension force in the sitting position and thickness of the quadriceps femoris muscle were also measured. The quadriceps femoris thickness, skewness, kurtosis, inverse difference moment, angular second moment, and muscle strength were significantly decreased in elderly participants versus those in the younger and middle-aged groups (P < .05). In contrast, the mean and sum of entropy were significantly decreased in the younger group compared with the middle-aged and elderly groups. Sonography has the capacity to quantitatively assess muscular morphologic changes due to aging and could be a valuable tool for early detection of musculoskeletal disorders.