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. 2025 Jun 11;12(2):e70306.
doi: 10.1002/jeo2.70306. eCollection 2025 Apr.

Measurement properties of the Swedish version of the Knee Self-Efficacy Scale: A Rasch analysis

Ramana Piussi  1   2 , Roland Thomeé  1   3 , Kristian Samuelsson  2   4 , Eric Hamrin Senorski  1   2   5
Affiliations

Measurement properties of the Swedish version of the Knee Self-Efficacy Scale: A Rasch analysis

Ramana Piussi et al. J Exp Orthop. .

Abstract

Purpose: This study aimed to evaluate measurement properties of the Swedish version of the Knee Self-Efficacy Scale 18 items version (K-SES18) in patients after anterior cruciate ligament (ACL) reconstruction using Rasch measurement theory (RMT).

Method: Data were extracted from Project ACL, a rehabilitation registry. Responses to the K-SES18 from 1307 patients (aged 15-50 years) at 12 months post-ACL reconstruction were analyzed. The RMT analysis assessed targeting aspects of reliability, response category thresholds, item hierarchy, overall and individual item fit, local dependency, differential item functioning (DIF) and unidimensionality.

Results: The use of RMT indicated that the K-SES18 present subscale exhibited high reliability (Person separation index = 0.904; Cronbach's α = 0.939) but also a potential ceiling effect (mean person location = 1.440). Disordered thresholds were observed in 11 out of 14 items, which indicates that, according to the RMT, patients might have some difficulties to distinguish between response categories. Item misfit was noted, which suggests multidimensionality. Subgroup analyses partially resolved local dependency but indicated distinct dimensions for daily activities, leisure activities and physical activities. The K-SES18 future subscale also demonstrated good reliability (PSI = 0.750; α = 0.783) but showed targeting issues and multidimensionality across items.

Conclusion: The main finding of this study is that the K-SES18, according to RMT, demonstrates strong reliability but has limitations in terms of measurement properties that possibly limit its clinical utility. The present and future subscales exhibit ceiling effects, disordered thresholds, and item misfit. Therefore, the K-SES18 might not be able to capture the full range of patients' knee self-efficacy after ACL reconstruction. These findings indicate that a scale refinement to enhance targeting, response sensitivity, and dimensionality is needed. Clinicians are therefore advised to interpret the subscale scores cautiously, acknowledging the multidimensional nature of the constructs measured.

Level of evidence: Level III.

Keywords: patient‐reported outcomes; psychometric properties; rasch analysis; rehabilitation outcomes.

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Conflict of interest statement

Author Kristian Samuelsson discloses he is a board member of Getinge AB (publ). The remaining authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Flowchart of inclusion.
Figure 2
Figure 2
Person‐item threshold distribution for the K‐SES18 present subscale, distribution of people (upper panel) and response category thresholds (lower panel) on the common logit metric (x‐axis; positive values = more positive knee self‐efficacy. K‐SES, Knee Self‐Efficacy Scale.
Figure 3
Figure 3
Threshold map; xx = disordered thresholds.
Figure 4
Figure 4
Inter‐items correlations matrix in K‐SES18 present. Green highlight: negative values above critical value; pink highlight: positive values above critical value. K‐SES, Knee Self‐Efficacy Scale.
Figure 5
Figure 5
Person‐item threshold distribution for the K‐SES18 future subscale, distribution of people (upper panel) and response category thresholds (lower panel) on the common logit metric (x‐axis; positive values = more positive knee self‐efficacy. K‐SES, Knee Self‐Efficacy Scale.
Figure 6
Figure 6
Inter‐item correlations matrix for items in K‐SES future. Green highlight: negative values above critical value; pink highlight: positive values above critical value. K‐SES, Knee Self‐Efficacy Scale.
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