Knee osteoarthritis and minimal important change for the nine-step stair climb test

INTRODUCTION: Stair-climbing tests (SCT) assess stair negotiation in knee osteoarthritis (OA). The minimal important change (MIC) is a measure of interpretability. The MIC of the nine-step SCT for patients with knee OA has not been established. In a secondary analysis from a randomised controlled trial, we aimed to estimate the MIC of the nine-step SCT in patients with knee OA after 12 weeks of neuromuscular exercise. METHODS: In a previously reported randomised controlled trial, knee OA patients not eligible for knee arthroplasty were randomised to a 12-week neuromuscular exercise intervention with/without additional low-dose strength training. SCT data were collected at baseline and after 12 weeks. Self-reported experience of change in the patient's knee problem was measured with the seven-point anchor question Global Perceived Effect Score (GPE) at 12 weeks. Among the 90 patients included at baseline, 72 had complete follow-up data. In this secondary analysis, an adjusted MIC estimate was calculated using predictive modelling. RESULTS: The mean SCT time at baseline was 12.6 (± 5.5) seconds, and the mean change in SCT at 12 weeks was 2.6 (± 3.3) seconds. The adjusted MIC value (95% CI) for improvement was 2.2 seconds (95% CI: 1.5; 3.0) for the nine-step SCT. CONCLUSIONS: The 2.2-second MIC value for the nine-step SCT in knee OA patients may be considered a first indicator of the magnitude of minimal improvement that the average patient would find important. FUNDING: None. CLINICALTRIALS: gov NCT03215602.