Validated scoring measures in morphoea can facilitate clinical trials.To ascertain the clinical significance of scores on the Localized Scleroderma Cutaneous Assessment Tool (LoSCAT) and identify the change in scores correlated with clinically meaningful change.A prospective study of 120 participants from the Morphea in Adults and Children (MAC) cohort was undertaken. Physician's subjective assessments of severity and of improvement were completed at each visit. Receiver operating characteristic analysis determined LoSCAT scores corresponding with mild, moderate and severe disease, and absolute and percentage changes in scores corresponding with improved or worsened disease activity or damage.Mild, moderate and severe activity corresponded with LoSCAT activity index (LoSAI) scores of 0-4, 5-12 and 13 and over, and with Physician's Global Assessment of activity (PGA-A) scores of 0-10, 11-30 and 31 and over. Mild, moderate and severe damage corresponded with LoSCAT damage index (LoSDI) scores of 0-10, 11-15 and 16 and over, and with PGA of damage (PGA-D) scores of 0-18, 19-30 and 31 and over. Improved activity was best indicated by LoSAI decrease of at least 2 points or 27·5%, or PGA-A decrease of at least 6 points. Improved damage was best indicated by LoSDI score decrease of at least 2 points. Worsening activity was best indicated by LoSAI increase of at least 2 points or 19·5%, or PGA-A increase of at least 4 points. Worsening damage was best indicated by LoSDI increase of at least 25·5%.The LoSCAT can be used to classify patients with morphoea by disease severity, and identify clinically significant improvement in activity. What's already known about this topic? The Localized Scleroderma Cutaneous Assessment Tool (LoSCAT) is a clinical tool that separately quantifies disease activity and damage in morphoea, and prior studies have demonstrated validity and reliability. What does this study add? The LoSCAT can be used to classify patients with morphoea by disease severity into mild, moderate and severe groups, and to identify clinically significant improvement in disease activity in patients with morphoea. The LoSCAT may be limited in its ability to detect clinically significant changes in disease damage.