Common Physical Examination Tests for Patellofemoral Instability Demonstrate Weak Inter-Rater Reliability

PURPOSE: The purpose of this study was to assess the inter-rater reliability of 3 common physical examination assessments, the Q-angle, J-sign, and apprehension test, used to evaluate patients presenting with recurrent lateral patellofemoral instability. METHODS: A consecutive sample of 38 subjects with recurrent lateral patellofemoral instability in 2013 were included in this reliability study. Two orthopaedic surgeons performed the physical examination maneuvers blinded to each other. The physical examination tests were performed bilaterally and included the Q angle, the J-sign, and the apprehension test. To measure the inter-rater reliability, an intraclass correlation coefficient (ICC 2,κ) was used for both legs independently for Q-angle measurements. A Cohen’s kappa was used to measure the inter-rater reliability for the J-sign and the apprehension test. RESULTS: The measurement of the Q-angle demonstrated poor reliability (ICC 2,κ 0.18-0.44). The assessment of the J-sign demonstrated fair to moderate reliability (κ = 0.31 – 0.41), and the evaluation of apprehension demonstrated fair to substantial reliability (κ = 0.30 – 0.65). All 3 clinical tests demonstrated substantial variability comparing the reliability on the right and left limbs. Assessment of the quality of apprehension demonstrated good agreement between the examiners. CONCLUSIONS: In this study of patients with recurrent lateral patellofemoral instability the common physical examination tests, Q-angle, J-sign, and apprehension demonstrated weak inter-rater reliability. These results indicate that these tests are not reliable for communication between health care practitioners or as evaluations for clinical research. LEVEL OF EVIDENCE: Level IV, therapeutic case series.