The dynamic function of the rabbit temporomandibular joint (TMJ) was analyzed through non-invasive three-dimensional skeletal kinematics providing essential knowledge for understanding normal joint motion. with respect to the rotational movement about the transverse axis showed a consistent relationship to within 0.05 mm/degree. The maximal translations of the incisors and condyles were also consistent within and between rabbits. With an understanding of the normal mechanics of the TMJ kinematics can be used to compare and understand TMJ injury and degeneration models. Keywords: temporomandibular joint 3 joint kinematics INTRODUCTION Some estimates suggest that over ten million Americans are affected by temporomandibular joint (TMJ) disorders (TMDs) (NIH and NIDCR 2010 Clinical symptoms of TMDs include jaw locking 2-Atractylenolide clicking on headaches joint pain and tenderness restricted range of motion painful mastication and deterioration of the disc and the articulating surfaces of the TMJ (Wilkes 1989 Clinical exams often used to diagnose TMDs only test the end positions of the teeth and do not focus on the travel path of the joint. It is important to understand the kinematics of the joint to determine if early changes in the function of the joint may suggest oncoming TMDs. Knowledge of dynamic TMJ function through three-dimensional (3D) skeletal kinematics is essential 2-Atractylenolide for understanding normal joint behavior and investigating the effects of injury or disease in the TMJ. Many factors contribute to joint motion including muscular causes passive structures constricting movement and dynamic physical forces such as contact gravity and inertia 2-Atractylenolide (Markolf et al. 1981 Schipplein and Andriacchi 1991 However little is known on how these factors combine for everyday movement making replication of kinematics hard (Tashman and Anderst 2003 3 visualization and measurement techniques are necessary to measure skeletal kinematics with high precision and accuracy. Numerous kinematic studies have been performed on humans many looking at the effects of partial and total joint replacement and other invasive treatments on joint motions (Baltali et al. 2008 Gallo 2005 Keller et al. 2012 Leiggener et al. 2012 Linsen et al. 2012 Palla et al. 2003 Voiner et al. 2011 Yoon et al. 2007 While incisal movement alone is not enough to understand the movement Dysf of the mandibular 2-Atractylenolide 2-Atractylenolide condyles (Naeije 2002 Travers et al. 2000 3 jaw tracking systems have provided more insight into condylar motion (Baltali et al. 2008 Gallo 2005 Keller et al. 2012 Leiggener et al. 2012 Linsen 2-Atractylenolide et al. 2012 Palla et al. 2003 Voiner et al. 2011 In-depth TMD patient studies have not been performed with these systems because it is usually hard to identify patients at early stages of dysfunction. The current 3D systems are beneficial for human patient studies but cannot be implemented in noncompliant animal models. Animal studies are uniquely suited for investigating the disease initiation and progression that cannot be completed and repeated in a patient study by enabling both mechanical interventions that may drive disease development and comprehensive invasive tissue assessment. In particular the rabbit model was chosen due to the numerous TMJ injury and degeneration models already established in the literature (Ali and Sharawy 1995 Almarza et al. 2011 Axelsson et al. 1992 Chaves et al. 2002 Shaw and Molyneux 1993 Timmis et al. 1986 Tominaga et al. 1999 Tominaga et al. 2000 Ueki et al. 2003 Rabbits also exhibit a grinding mastication similar to that of humans (Morita et al. 2008 Several studies have previously collected normal rabbit kinematics; however most carried out were invasively and only focused on incisal movement (Huff et al. 2004 Inoue et al. 2004 Inoue et al. 1989 Langenbach et al. 2001 Morimoto et al. 1985 Schwartz et al. 1989 Tominaga et al. 2000 Weijs et al. 1989 Weijs and Dantuma 1980 Weijs et al. 1989 Yamada and Haraguchi 1995 Yamada et al. 1988 Yamada et al. 1990 instead of also understanding condylar movement (Morita et al. 2008 Non-invasive 3D x-ray imaging systems have been developed to combine x-ray videos with 3D morphology from bone scans and have been extensively validated in human and animal joints (Bey et al. 2008 Bey et al. 2006 Brainerd et al. 2010 Tashman and Anderst 2003 Tashman et al. 2007 including one study of normal minipig mastication (Brainerd et al. 2010 Our study investigated the dynamic nature of the TMJ condyle with respect to the fossa as well as the incisor relationship in rabbits. The objective of this study was to determine and evaluate repeatable.