The kneeling view: Evaluation of the forces involved and side-to-side difference Leonardo Osti a, 1 , Rocco Papalia b , Paola Rinaldi c , Vincenzo Denaro b , John Bartlett d , Nicola Maffulli e, ⁎ a Unit of Arthroscopy and Sports Trauma Surgery, Hesperia Hospital, Via Arquà 80/b, Modena, Italy b Department of Orthopaedic and Trauma Surgery, Campus Biomedico University of Rome, Via Alvaro del Portillo 200, Rome, Italy c Department of Engineering, University of Bologna, Viale Risorgimento, 2 40136 Bologna, Italy d Warringal Hospital, 216 Burgundy Street, 3084 Heidelberg Vic, Australia e Centre for Sports and Exercise Medicine, Barts and The London School of Medicine and Dentistry, Mile End Hospital, 275 Bancroft Road, London E1 4DG, England, United Kingdom abstract article info Article history: Received 19 March 2009 Received in revised form 14 April 2009 Accepted 16 April 2009 Keywords: Posterior knee laxity Imaging Clinical measurement The kneeling view is a method to objectively measure posterior knee laxity. However, the actual amount of load applied and the reliability of this method in term of side to side difference are not known. We studies these issues in a group a 25 healthy volunteers who underwent measurements of posterior knee laxity in both knees. A standard digital scale was positioned under both kneeling supports to measure the actual amounts of posterior displacement forces applied. We measured the mass of the subject, the side-to-side difference of the weight applied into anterior aspect of the tibia, and the ratio weight of the subject/ amount of posterior displacement load applied. The average amount of forces applied was at least 75% of the body weight of each subject, with a side-to-side variability of 3.3% of the weight applied. The kneeling view can be considered, in terms of forces applied, a reliable and reproducible alternative method for the routine radiographic evaluation of the posterior knee laxity. © 2009 Elsevier B.V. All rights reserved. 1. Introduction In the last 20 years, several non-invasive techniques have been developed to assess the posterior displacement of the tibia over the femur by stress radiography as indirect evidence of posterior cruciate ligament (PCL) injury, and to quantify objectively the degree of PCL deficiency [1–3]. These methods are performed using different forces provided by an external device [4], muscle contraction [5], or gravity [6–8]. Fukubayashi et al. [9] introduced the concept that the amount of posterior tibia displacement is force-dependent. In fact, the extent of posterior translation of the knee obtained by a stress radiography technique hinges on the amount of forces applied, and on the resistance to such load by the ligaments and meniscocapsular restraints and strength of the muscles around the knee. Therefore, the higher the amount of force applied on the knee the larger the resultant displacement [10]. Apart from the Telos technique [11], the actual amount of forces acting on the tibia are unknown. Noyes et al. reported that with a PCL deficient knee the maximum posterior displacement is between 70 and 90° of flexion [12]. Therefore, kneeling with the knee kept at 90° of flexion is an appropriate angle for stress radiography, and previous studies reported that kneeling is alternative economic method to assess posterior knee laxity with a direct load applied [11,13]. We assessed the actual amount of force imparted on the anterior aspect of the upper tibia to produce posterior displacement using the kneeling view technique. 2. Materials and methods A group of 25 healthy volunteers was enrolled in the study. The exclusion criteria included knee osteoarthritis, inflammatory arthro- pathies, previous knee injury or knee operations, patellar tendino- pathy, and Osgood–Schlatter lesion. There were 20 men and five women with an average age of 22.3 (Range 20–25). 2.1. Technique of measurement A commercially available digital scale (Seca 888, Seca Corporation, Hanover, MD, USA) with automatic calibration, an upper limit of 160 kg and a graduation of 200 g, was fixed under both sides of the 90° kneeling support constructed according to Barlett and Osti [13] (Figs. 1, 2). The apparatus allowed a comfortable kneeling position to be maintained and to apply a direct load to the knee joint distal to the tibial tubercle [13]. The patella and femoral condyle were unsupported over the edge of the bench. The patients were asked not to actively contract the posterior muscles of the thigh. Patients were instructed to hold the knee (one at a time) still for 15 s so that it was possible to read the weight value, first in one knee and then in the other. The procedure was repeated three times for The Knee 16 (2009) 463–465 ⁎ Corresponding author. E-mail address: n.maffulli@qmul.ac.uk (N. Maffulli). 1 Fax: +39 059394840. 0968-0160/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.knee.2009.04.010 Contents lists available at ScienceDirect The Knee