Sonographic Evaluation of the Degree of Medial Meniscal Extrusion During Thessaly Test in Healthy Knees

Abstract ObjectiveThe Thessaly test is a commonly used orthopedic test for meniscus tear evaluation. The study’s objective is to evaluate the degree of medial meniscal extrusion during different loading phases of the Thessaly test. MethodsA convenience sample of 60 healthy knees (35 participants) was examined. Sonographic measurement of the degree of physiologic extrusion of the medial meniscus deep to the medial collateral ligament was taken by two examiners at six different loading phases: supine, standing, 5° knee-flexion with internal (IR)/external (ER) rotation and 20° knee-flexion with IR/ER. The difference in meniscal extrusion by knee position was compared with ANOVA. Interrater reliability assessment was analyzed using intraclass correlation coefficient. ResultsThe mean meniscal extrusion for each position was - supine: 2.3±0.5mm, standing: 2.8±0.8mm, 5° IR: 2.3±0.9mm, 5° ER: 2.4±0.7mm, 20° IR: 1.9±0.8mm, and 20° ER: 2.3±0.7mm. Significant increase in extrusion was observed from supine to standing (p<0.05) and from 20° IR to 20° ER (p=0.015). Significant decreased measurement was observed from standing to 5° IR (p<0.05), 5° ER (p<0.05), 20° IR (p<0.05) and 20° ER (p<0.05). There is no significant change between 5° IR and 5° ER (p=1.0). Interrater reliability of the measurements across the six positions was poor to moderate (0.35-0.57, p<0.05). ConclusionOur study’s novel findings showed clear dynamic changes during Thessaly test, which implies increase in compressive stress across the medial meniscus and a potential mechanism for pain generation during this test. Further testing is needed to address the poor-moderate reliability and confirm findings.