Is Fear of Movement (FoM) in sports related activities a latent trait?: the item response model applied to the Photographic Series of Sports Activities for Anterior Cruciate Ligament Rupture (PHOSA-ACLR).

Abstract Background. Fear of Movement is an important factor predicting return to sports in Anterior Cruciate Ligament Reconstruction (ACLR). Fear for specific ACLR related movements can be addressed measuring the Photographic Sports Activities for ACLR (PHOSA-ACLR). This study was conducted to determine whether Fear of Movement assessed using the PHOSA-ACLR is a latent trait, and to analyse differences in PHOSA-ACLR in athletes with or without an ACL rupture. Methods. Data from three groups of participants were included in this study: 1) ACLR patients participated in a previous study measuring psychological dimensions after ACLR (n = 58); 2) first year physical therapy students at the HAN University of Applied Sciences (n = 169), and 3) junior football players that were enrolled in a training programme of the Professional Soccer club Vitesse (Arnhem) (n = 30). All participants completed the PHOSA-ACLR (scale score 0-10), and questions related to demographics. ACLR patients completed additional questionnaires to assess functioning and Fear of Harm. PHOSA-ACLR items were analysed with Item Response Theory using the Graded Response Model (GRM). Differences between three groups of participants were analysed using Univariate Analysis of Variance. Results. The two-parameter GRM with both location and discrimination (-2LL = -5485.05) showed a significantly better fit than the one-parameter model (-2LL = -5515.36), Common.EditSubmissionSteps.Transform.EquationText (1) = 30.31, p = 0.00). The items of the PHOSA-ACLR thus constitute a latent trait. The three groups of participants differed in reported fear of movement assessed with the PHOSA-ACLR after controlling for covariates gender and age. Physical therapy students reported higher levels of fear of movement compared to either ACLR patients and healthy soccer players (respectively 4.9 (95%CI 4.6-5.3); 3.6 (95%CI 2.5-3.7); 2.6 (95%CI 1.6-3.6)). Conclusion. PHOSA-ACLR items constitute a latent trait of fear of movement for ACLR specific movements. Contrary to expectations, PHOSA-ACLR is higher in first year physiotherapy students compared to patients rehabilitating from ACLR, and healthy junior soccer players. The PHOSA-ACLR might be useful for clinicians to identify high levels of fear of movement related to ACLR, and provide a tool to help the patient overcome fear of movement using exposure techniques.