Do cervical sagittal alignment profiles affect pain and disability in forward head posture? a cluster-based cross-sectional study

Purpose To identify naturally occurring cervical sagittal alignment clusters in individuals with forward head posture (FHP) using a comprehensive multivariate radiographic profile, and to determine whether the resulting clusters differ in neck pain intensity and functional disability. Methods Cross-sectional study of 75 adults (48 males, 27 females; aged 18–40 years) with clinically confirmed FHP, defined as a craniovertebral angle (CVA) below 50°. Five alignment parameters — CVA, cervical sagittal vertical axis (CSVA), T1 slope (T1S), Spinocranial Angle (SCA), and Cobb angle — were measured using standardized lateral photography and digital radiography. Neck pain intensity and functional disability were assessed using the Pain Rating Scale (PRS) and Neck Disability Index (NDI), respectively. Data-driven cluster analysis was applied to identify alignment subgroups, and between-cluster differences in clinical outcomes were examined using appropriate parametric and non-parametric tests. Results Two distinct clusters emerged: Cluster 1 ( n = 44, Lower Radiographic Displacement) and Cluster 2 ( n = 31, Higher Radiographic Displacement). T1S, SCA, Cobb angle, and CSVA were significant cluster discriminators (all p ≤ .009); CVA did not differentiate clusters ( p = .155). Despite robust alignment differences, neither pain intensity ( p = .653) nor functional disability ( p = .833) differed significantly between clusters. Conclusion Radiographically distinct cervical sagittal alignment profiles showed no statistically significant or clinically meaningful differences in neck pain intensity or functional disability in community-based FHP populations within the mild-to-moderate symptom range. CVA failed to discriminate alignment subgroups, supporting the potential added value of multivariate radiographic profiling over single-angle photographic classification.