Rotator cuff-related shoulder pain (RCRSP) is a common complaint in the general population. Pain catastrophizing plays a crucial role in the experience and management of chronic musculoskeletal pain, including rotator cuff-related shoulder pain (RCRSP). The Pain Catastrophizing Scale (PCS) is widely used to assess catastrophic thinking related to pain, but its construct validity and responsiveness in individuals with RCRSP require further investigation.

To evaluate the construct validity and responsiveness of the PCS in individuals with RCRSP.

This was a cross-sectional study approved by a research ethics committee. This study included individuals aged 18 years or older, with shoulder pain for at least 3 months, and pain intensity of 3 or higher on an 11-point numerical rating pain scale (NPRS) during arm elevation. The construct validity was analyzed through hypothesis testing. This study hypothesizes that the rumination, magnification, and helplessness subscales and total score of PCS are moderately (r > 0.40) and positively associated with pain intensity, upper limbs disability (quick version of Disabilities of the Arm, Shoulder, and Hand (QuickDASH) questionnaire), and fear of movement (Tampa Scale for Kinesiophobia (TSK)). . Validity was deemed acceptable if = 75% of the hypotheses were confirmed. Responsiveness was analyzed in individuals treated for eight weeks using effect size (ES), standardized response mean (SRM), and area under the curve (AUC-ROC). ES and SRM values were interpreted as small (< 0.50), moderate (0.50–0.80), or large (> 0.80). The Global Rating of Change (GROC), used as an external anchor, classified individuals as having "significant improvement" or "mild/no improvement" (cut-off = 4). AUC > 0.70 indicated adequate responsiveness. Statistical analyses were conducted using SPSS 23.0, with a significance level of 0.05.

The validity analysis included 64 participants, while the responsiveness analysis involved 59. The mean age was 37.5 ± 12.3 years for validity and 37.7 ± 12.6 years for responsiveness. The mean symptom duration was 12.0 ± 6.27 months in both analyses, and the mean pain intensity was 6.9 ± 2.0 for validity and 6.9 ± 1.9 for responsiveness. Construct validity analysis showed that the PCS met 83% of the proposed hypotheses. The PCS exhibited a significant moderate correlation with TSK, NPRS, and QuickDASH, except for the rumination and magnification subscales, which showed a weak correlation. The rumination, helplessness subscales, and total PCS score demonstrated a large effect size and responsiveness, while the magnification subscale showed a moderate effect. All subscales and the total PCS score had an AUC above 0.7, indicating good responsiveness.

The PCS demonstrated adequate construct validity and responsiveness in assessing individuals with chronic RCRSP.

The PCS demonstrated adequate validity and responsiveness for assessing pain catastrophizing in individuals with chronic RCRSP. Its use can aid clinicians in identifying maladaptive pain-related thoughts and monitoring treatment progress.