Content Validity of the Forgotten Joint Score (FJS-12) for Total Ankle Replacement

Research Type: Level 4 – Case series Introduction/Purpose: The Forgotten Joint Score (FJS-12) measures hip and knee patients’ ability to forget their replaced joint in everyday life. This study evaluates whether the FJS-12 includes the appropriate items for total ankle replacement (TAR) patients to ensure findings are accurate and meaningful. Methods: An internet-based, cross-sectional survey of TAR patients and clinicians with TAR experience examined the relevance, comprehensiveness, and comprehensibility of the FJS-12, consistent with COSMIN methodology for content validity. Respondents rated the relevance of FJS-12 items and provided input using open-ended questions on additional necessary content. Cognitive interviews were conducted with 8 patients to evaluate its comprehensibility. Items were considered relevant if ≥70% patients endorsed them. Analysis involved descriptive statistics and content analysis. Results: Sixty-one respondents (54 patients, 12 clinicians) participated. The mean age of the patient sample was 65.3 years, 66.7% were male, 61.1% were retired, and average follow-up length was 2.2 years. Of the 12 FJS-12 items, 3 items were endorsed as relevant, 5 fell just below the threshold, and 4 items were endorsed by < 50% patients. Clinicians endorsed 11 items, with 1 endorsed by only 50.0% of clinicians. Clinicians and patients recommended new content, and patients provided insight into poorly performing items. Conclusion: The FJS-12 lacks content validity for TAR patients. Some items lack sufficient relevance according to patients, and content is missing to allow comprehensive measurement of TAR patients’ ability to forget their joint replacement in daily life. A new FJS-12 will be developed based on this work and undergo psychometric testing in a TAR population.