Translation, cross-cultural adaptation, and psychometric properties of the Persian version of the Pain Severity Scale in patients with patellofemoral pain

Purpose: To translate the Pain Severity Scale (PSS) into Persian (PSS-Persian) and study its psychometric properties in patients with patellofemoral pain (PFP). Materials and methods: The psychometric properties of 112 patients with PFP were evaluated using a questionnaire. The structural validity, construct validity, reliability, internal consistency, and floor and ceiling effects were evaluated. Convergent validity was examined using Pearson's correlation coefficient between the PSS-Persian, Oxford Knee Score (OKS), Kujala Anterior Knee Pain Scale (AKPS), and Knee Outcome Survey Activities for Daily Living (KOS-ADL). Results: Good internal consistency was found (Cronbach's alpha = 0.889), and if the item was deleted varied from 0.868 to 0.886. The intraclass correlation coefficient (ICC) for test-retest reliability was 0.784. The factor loading for each item was >0.55. The PSS-Persian score showed a moderate correlation with the AKPS (r = -0.315, p = 0.001). The PSS-Persian score was also significantly correlated with the OKS (r = -0.231, p = 0.004) and KOS-ADL (r = -0.226, p = 0.017). Conclusion: The data showed that the cultural adaptation process was successful. The PSS-Persian has acceptable measurement properties and is suitable for use in epidemiological, rehabilitation, and clinical contexts of patients with PFP in the Persian population.