RESUMO
OBJECTIVE: To develop a scale for estimating the severity of patellofemoral pain syndrome (PFPS) and to determine its reliability and validity. DESIGN: The PFPS Severity Scale (PSS) was developed following a literature search, input from clinicians, and pilot testing in people with PFPS. The final version of the instrument encompasses 10 statements regarding PFPS pain in a visual analogue format. Reliability and validity of the new scale were determined in a PFPS population. SETTING: All testing was performed at the Canadian Forces Base Kingston, Physiotherapy Department. SUBJECTS: Twenty-nine military subjects (7 female) between the ages of 20 and 48 (32 years +/- 8.9) with subjective and objective findings consistent with PFPS were recruited. Twenty-four of the participants (6 female, 31.8 years +/- 9.4) participated in the reliability phase of the study. METHODS: Reliability of the PSS was determined by comparing the scores obtained on two test days (24 hours apart). Convergent validity of the PSS was determined by comparing data from the PSS with two established knee scales: the WOMAC (Western Ontario and McMaster Universities) Osteoarthritis Index and the Hughston Foundation subjective knee scale. RESULTS: Test-retest reliability was excellent (Spearman's rho = 0.95, p < 0.0001). The correlations between the PSS and the WOMAC and Hughston scales were strong (rho = 0.72 and 0.83, p < 0.001 respectively). CONCLUSIONS: The PSS is reliable and has demonstrated convergent validity making it a useful tool for monitoring rehabilitative or surgical outcomes in clients with PFPS.