IRBM 31 (2010) 302–308 Original article In vitro analysis of varus-valgus laxity of the knee joint: Comparison of clinical evaluation with measurements using a reference motion analysis system Analyse in vitro de la laxité en varus-valgus du genou : comparaison entre l’évaluation clinique et la mesure objective par un système d’analyse du mouvement de référence R. Testa a,b,c,d,∗ , J. Chouteau a,b,c,d , R. Philippot e,f , L. Cheze a,b,c , M. Fessy a,b,c,d , B. Moyen a,b,c,d a Université de Lyon, 69622, Lyon, France b LBMC, INRETS, UMR T9406, 69625, Bron, France c Université Lyon-1, 69100 Villeurbanne, France d Service de chirurgie orthopédique, centre hospitalier Lyon-Sud, hospices civils de Lyon, chemin du Grand-Revoyet, 69495 Pierre-Bénite cedex, France e Laboratoire de physiologie de l’exercice, EA 4338, Saint-Étienne, France f Service de chirurgie orthopédique, CHU de Saint-Étienne, Saint-Étienne, 42055 cedex 2, France Received 28 April 2010; received in revised form 2 June 2010; accepted 27 October 2010 Available online 3 December 2010 Abstract Introduction. – Numerous measurement devices can help clinicians during the knee examination. However, manual evaluation still remains routinely used to assess the knee laxities. The present study evaluated how accurate was a clinician for a varus-valgus stress test. We compared the clinician evaluation to the objective measurement of the knee movements during the same test session. Methods. – We studied six fresh-frozen anatomical lower limbs. The clinician performed a varus-valgus stress test in extension and at 25 ◦ flexion. The limbs were equipped with intracortical pins in femur and tibia, and spherical retro-reflecting markers were glued on the pins. Objective knees movements were measured by means of a Motion Analysis ® system (Motion Analysis Corporation, Santa Rosa, CA, USA). Two statistical analyses were performed. A single sample t-test was first used to verify the required 25 ◦ flexion. Then, a multivariate anova was performed to analyse the varus-valgus laxity under the fixed factors of measurement method and flexion of the knee. Results. – The results for varus-valgus and total laxity of the clinician always exhibited a greater variability than objective measurements of the device. Test condition is a factor of grouping differences for Valgus and for global mediolateral laxity. Statistical analysis revealed that the objective measurement was able to show a difference between extension and 25 ◦ flexion for global mediolateral laxity, whereas the clinician was not. Discussion. – The clinician was relatively accurate in his manual evaluation. However, we demonstrated that a measurement device could clearly help clinician to exhibit differences in laxity. This can be very useful to compare a knee to itself in two successive conditions, e.g., before and after a surgery. © 2010 Elsevier Masson SAS. All rights reserved. Keywords: Accuracy; In vitro; Joint instability; Knee Résumé Introduction. – De nombreux systèmes existent pour aider le clinicien lors de l’examen du genou. Toutefois, l’examen manuel est encore couramment utilisé pour l’évaluation des laxités. La présente étude a évalué quelle était la précision du clinicien lors d’un test standard de varus-valgus forcé. Nous avons comparé l’évaluation du clinicien par rapport aux mouvements réels du genou. Méthode. – Nous avons utilisé six pièces anatomiques de membres inférieurs récemment congelés. Le clinicien a réalisé un test de varus-valgus forcé en extension, puis à 25 ◦ de flexion. Les membres étaient équipés de broches fixées dans le fémur et dans le tibia. Des sphères rétro-réfléchissantes étaient collées sur ces broches. Les mouvements du genou étaient obtenus à l’aide d’un système Motion Analysis ® (Motion Analysis Corporation, ∗ Corresponding author. E-mail addresses: rtesta@free.fr, rodolphe.testa@chu-lyon.fr (R. Testa). 1959-0318/$ – see front matter © 2010 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.irbm.2010.10.005