BACKGROUND: The foot and ankle are frequently affected in rheumatic and musculoskeletal diseases (RMDs), yet there is a lack of high-quality evidence to determine the effectiveness of treatments. Outcomes in research are often inconsistently measured, impeding evidence synthesis. Additionally, clinical decisions are based on research outcomes, but these are not always regarded as important by people with RMDs. This study aimed to determine domains of importance to people with RMDs who have experienced foot and ankle disorders, and aid in developing a standardised core outcome set (COS) to address these issues. METHODS: Participants from four continents (Europe, Africa, Australia, North America) were recruited to semi-structured interviews through clinical departments and electronic mailing lists. Analysis was conducted using a mixed deductive/inductive approach to the framework method. Patient research partners co-produced the interview schedule and recruitment materials, and co-interpreted results. RESULTS: Fifty-six participants (age range 27 to 76 years
66 % female), with foot and ankle disorders in a variety of RMDs (including inflammatory arthritis, osteoarthritis, crystal arthropathies, connective tissue diseases), were interviewed. Sixteen domains were described by participants: pain, physical function, fatigue, deformity, skin and nail health, swelling, temperature, numbness, poor circulation, cramping, activities/participation, footwear impact, psychological impact, sleep, healthcare utilisation and personal expenses. Most domains were considered important to participants regardless of RMD or geographic location. CONCLUSIONS: Foot and ankle disorders have far-reaching consequences for people with RMDs. This large qualitative study provides a foundation for achieving international consensus on a core outcome set for foot and ankle disorders in RMDs, to improve the quality of evidence demonstrating effectiveness of treatments.