Objective: Few studies have investigated the relationship between spinal muscle fatty degeneration and vertebral compression fracture (VCF) progression. This study investigated the associations among spinal muscle fatty degeneration, functional support of the spinal muscles, and VCF progression.Methods: We retrospectively evaluated 49 consecutive elderly patients over 65 years of age who had VCFs between 2013 and 2020. Change in height loss was defined as the difference in height loss in vertebral collapse between the initial and >6-month follow-up visits. Fatty infiltration of the paraspinal and psoas muscles was measured using T2-weighted magnetic resonance imaging at L3 and L4.Results: The VCF height loss change was 6.53±4.9 mm. The cross-sectional area of the paraspinal muscle was 2,418±496 mm2. The fatty infiltration rate of the paraspinal muscle was 4.46%±1.7%. Mild VCF height loss (a change o≤9 mm) was found in 36 patients (group 0), while severe height loss (a change >9 mm) was observed in 13 patients (group 1). The paraspinal-to-psoas muscle ratio was 2.51 in group 0 and 3.33 in group 1 (P<0.002). The paraspinal muscle mass (P<0.02), bone mineral density (P<0.05), and paraspinal-to-psoas muscle mass ratio (P<0.01) affected VCF progression. The odds ratio of the paraspinal-to-psoas muscle ratio was 4.39.Conclusion: The paraspinal-to-psoas muscle ratio strongly influences VCF progression. In patients with VCF, progression can be predicted using the paraspinal-to-psoas muscle ratio before ambulation.