Haptic Visual and Superimposed Digital Imaging Analysis Improves the Interrater Reliability of J-Sign Assessment in Patients with Patellofemoral Instability: A Prospective Diagnostic Study

<b>Background:</b> J-sign assessment is increasingly important for decision-making in patients with patellar instability. However, the low interrater reliability of the J-sign evaluation has raised concerns. The aim of this study was to investigate whether haptic visual assessment or superimposed digital imaging analysis might improve interrater reliability. <b>Methods:</b> In 51 patients with ≥ 1 patellar dislocation, J-sign grading was assessed by two experienced observers via three different methods: (i) plain visual evaluation; (ii) combined haptic visual assessment, including palpation of the medial and lateral patellar facets with the thumb and index finger during active knee joint motion; and (iii) a digital photo application tool using superimposed digital imaging analysis obtained at 90° of flexion-knee joint flexion and full extension. <b>Results:</b> For the visual assessment of the J-sign, the interrater reliability was fair, with κ = 0.39 ± 0.11 [0.18-0.6]. The interrater reliability of the haptic visual assessment and the photo application reached a good level of agreement, with κ = 0.89 ± 0.05 [0.8-0.98] and κ = 0.85 ± 0.05 [0.74-0.95], respectively. <b>Conclusions:</b> Plain visual evaluation of the J-sign revealed fair interrater reliability. The haptic visual assessment of the J-sign and the digital photo application tool yielded good interrater reliability. The results indicate that haptic visual assessment of J-sign should be implemented in daily clinical practice and used to communicate findings between and among physicians and studies.