OBJECTIVE:To assess the comparative responsiveness of outcome measures used for the assessment of pain and function in individuals with first metatarsophalangeal joint osteoarthritis (1st MTPJ OA). METHODS:Eighty-eight people (mean age [SD] 57.2 [10.2] years) with 1st MTPJ OA who participated in a randomised trial completed the Foot Health Status Questionnaire (FHSQ), the Foot Function Index Revised Short Form (FFI-RS), and 100 mm visual analog scales (VAS) of pain and stiffness at baseline and 12 weeks. Responsiveness of the subscales for each outcome measure was determined using paired t-tests, Cohen's d, the standardised response mean (SRM), and the Guyatt index (GI). Sample size estimations were calculated based on minimal important differences (MIDs). RESULTS:All outcome measures were sensitive to change and demonstrated at least medium effect sizes. Three outcome measures exhibited large or very large effect sizes for Cohen's d, SRM, and GI: the FHSQ pain subscale (d=1.03; SRM=1.10, GI=1.30), the FFI-R pain subscale (d=1.09; SRM=1.05, GI=1.73), and the 100 mm VAS of pain severity while walking (d=1.22; SRM=1.07, GI=1.78). Sample size calculations indicated that between 20 and 33 participants per group would be required to detect MIDs using these measures. CONCLUSION:The FHSQ pain subscale, FFI-RS pain subscale, and the 100 mm VAS of pain severity while walking are the most responsive outcome measures for the assessment of pain and function in individuals with 1st MTPJ OA. These findings provide useful information to guide researchers in selecting appropriate outcome measures for use in future clinical trials. This article is protected by copyright. All rights reserved.