OBJECTIVE: To investigate how a global rating of change (GROC) score corresponds to change in Knee injury and Osteoarthritis Outcome Score (KOOS) subscales in people with patellofemoral pain (PFP). DESIGN: Secondary analysis of data from 3 clinical trials. METHODS: Four hundred ninety adolescents (10-18 years old) and adults (19-40 years old) with PFP completed KOOS (5 subscales, 0-100) at baseline and 3-month follow-up as well as GROC at 3-month follow-up. GROC category descriptors were mapped to 5 categories: worse, no change, a bit better, better, and much better. Gaussian approximation was then used to calculate the change in KOOS scores for each GROC category. RESULTS: Due to overlap between KOOS scores in "no change" and "a bit better," all analyses were performed on 4 categories. For all KOOS subscales, patients who reported being "worse" had negative KOOS scale change scores (≤ -2); patients reporting "no change" had KOOS scale change scores that ranged from -5 to 14; and patients feeling "better" or "much better" had positive KOOS scale change scores that ranged from 4 to 26 and ≥16, respectively. CONCLUSION: When patients with PFP reported feeling "worse," "better," or "much better," there was a small-to-substantial change across the different KOOS scales. This is in contrast to no difference between reporting "a bit better" or "no change" in KOOS. When patients say they feel a little better, clinicians should be less confident about whether change has truly occurred. J Orthop Sports Phys Ther 2024;54(10):657-671. Epub 25 July 2024. doi:10.2519/jospt.2024.12120.
Keywords: anterior knee pain; knee injuries; patient-reported outcome measure; questionnaire.