The Michigan Hand Questionnaire (MHQ) is a commonly used evaluation for hand problems, but previous work reports conflicting evidence regarding the subscale structures. Rasch analysis uses probabilistic modeling of items and responses: if scale items can be fit to the Rasch model, it provides evidence of construct validity and interval-level measurement for precise statistical estimates. We conducted Rasch analysis on the MHQ to evaluate model fit, unidimensionality of the subscales, bias across person factors, and conversion to interval metrics.We conducted a secondary Rasch analysis of MHQ data from 924 persons with thumb basal joint osteoarthritis using the RUMM2030 software. Modeling was based on responses for the most affected hand and person factors including age, sex, type of work, whether the dominant side was the most affected, and surgical status. The analysis plan followed the published recommendations for examinations of person and item fit, with iterative adjustments as required.A total of 11 of the 37 items required rescoring to create orderly progression of scoring thresholds. Only the overall hand function and pain subscales could be fit to the Rasch model, demonstrating unidimensionality and good reliability of fit estimates. Dividing the activities of daily living subscale into unilateral and bilateral activities also allowed unilateral activities to fit the model. Persistent misfitting in other subscales suggested local dependency and response bias across multiple person factors.This Rasch analysis of the MHQ raises concerns regarding the validity and fundamental measurement properties of this widely used outcome evaluation when used as a summary score.