Background and significance: This study measured the change in tarsal kinematics associated with hallux valgus deformity. The condition is a progressive foot deformity characterized by abduction of the hallux and corresponding adduction of the first metatarsal (ray). The theory advanced for testing was that collapse of the arch initiates deformity. Research Methods: Data was collected on cadaver feet (N = 9) and human subjects (N = 20). The study culminated in using weightbearing imaging methods. Subjects stood to simulate gait midstance (MS), heel off (HO), and terminal stance (TS) in an open-upright MR scanner. From the imaged data, selected bones were reconstructed and foot posture and joint motion were measured. Analysis: A mixed effect ANOVA model compared the variables tested between group (hallux valgus vs. controls) and across conditions (MS, HO, TS). In addition, correlation techniques assessed the relationship in arch angle (height) to the change in first ray adduction evaluated across gait events. Results: The calcaneus everted 7° more (P < 0.05) in subjects with hallux valgus as compared to controls. The first ray adducted 10° more (F = 44.17, P < 0.001) in subjects having deformity, with orientation of the first ray axis inclined 23° during middle stance as compared to 6° in controls. Arch angle did not differ between groups (P = 0.46). Additionally, no significant relationship (R2 ≤ 0.04) was found in kinematic variables in vivo but when testing cadavers, a negative relationship (r = -0.73) was identified between arch height and vertical tilt of the first ray axis. Discussion and conclusion: Results, in part, support theory and complement research. Inclination of the first ray axis may contribute to adduction of the first ray.