Correlation between cervical instability and neck muscle changes in middle-aged and young adults

• Cervical instability in middle-aged and young adults is associated with reduced relative cross-sectional area and increased fat infiltration in deep posterior cervical muscles. • C4/5 angular displacement negatively correlates with the relative cross-sectional area of deep posterior cervical muscles, indicating a potential biomechanical link. • Patients with cervical instability exhibit greater C4/5 horizontal and angular displacements, and smaller cervical curvature compared to healthy controls. • Deep posterior cervical muscle changes may serve as early indicators for prevention and intervention of cervical instability in this population.