The present study was undertaken to assess the comparative responsiveness of outcome measures used for the assessment of pain and function in individuals with osteoarthritis (OA) of the first metatarsophalangeal (MTP) joint.
Eighty-eight patients (mean ± SD age 57.2 ± 10.2 years) with OA of the first MTP joint who participated in a randomized 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 coefficient, the standardized response mean (SRM), and the Guyatt index (GI). Sample size estimations were calculated based on minimal important differences (MIDs).
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 coefficient, the SRM, and the GI: the FHSQ pain subscale (d = 1.03; SRM 1.10, GI score 1.30), the FFI-RS pain subscale (d = 1.09; SRM 1.05, GI score 1.73), and the 100-mm VAS of pain severity while walking (d = 1.22; SRM 1.07, GI score 1.78). Sample size calculations indicated that between 20 and 33 participants per group would be required to detect MIDs using these measures.
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 OA of the first MTP joint. These findings provide useful information to guide researchers in selecting appropriate outcome measures for use in future clinical trials.