OBJECTIVE : Chronic musculoskeletal pain and disability is common in adults with arthrogryposis multiplex congenita (AMC), but validated outcome measures of its related disability are lacking. This study aimed to determine the content and construct validity of the Oswestry Disability Index (ODI) for an AMC-appropriate low-back and lower-extremity pain-related disability questionnaire. METHODS : A mixed methods approach was used to investigate the nature of AMC-related low-back and lower-extremity pain and disability. We included 50 adults with AMC from an international arthrogryposis study. Participants completed 5 pain and disability questionnaires and an interview. Content and construct validity of the ODI in the AMC population was assessed by the proportion of participants who stated ODI domains during the open-ended interview and by R2 values and Pearson's correlation coefficients (r-values), respectively. RESULTS : The content and construct validity of the ODI were considered moderate to high for measuring low-back pain and lower-extremity disability in the adult AMC population. Participants independently identified many activities of daily living (67%), such as walking, standing, personal care, sitting, lifting and sleeping, already included in the ODI. R2 values were>0.25 for all 3 measures, demonstrating the strength of construct validity of the ODI in individuals with AMC. CONCLUSIONS : The ODI is a valid outcome tool for low-back and lower-extremity pain-related disability for patients with AMC. Upper-extremity issues were not addressed by the ODI, which will be further addressed in future research.