Temporomandibular joint (TMJ) disorders affect over 10 million people in the US with an annual economic cost of more than $4 billion. Due to intriguing etiological factors of TMJ disorders, objective and accurate diagnosis is difficult and so is with the treatment. Consequently, there is the high recurrence rate. To make the situation even worse, many other types of diseases, including cancer, share symptoms and signs with TMJ disorders. Early non-invasive, objective, subject-specific and accurate diagnosis is vital because incorrect or delayed diagnosis can cause patients to miss optimal treatment times, increase unnecessary therapy expenses and even endanger patients’ lives. The gold standard diagnostic criteria for TMJ disorders (DC/TMD) largely depend on subjective decisions, and therefore, it is necessary to develop a patient specific, non-invasive, and quantitative assessment system, to identify possible risk indicators for the objective early diagnosis of TMJ disorders and to determine their etiological biomechanical mechanisms by investigating the underlying biomechanical and transport pathophysiology of these indicators. As a result, significant advances in biomechanics and nutrient supply research are essential for early diagnosis and management. Common symptoms of joint sounds, limited or asymmetrical jaw movement, teeth misalignment, pain in the muscle, jaw or neck and jaw muscle stiffness indicate that an objective TMJ disorders diagnosis is necessary and should include TMJ muscle, motion and morphology assessment. Also, compared to other well-developed joint systems such as knee, glenohumeral and hip joints, TMJ has received less attention in biomechanics research because of the joint’s complexity in anatomy, neuromuscular recruitment and motion. The direct in vivo experimental measurement for articular space, contact force, stress distribution and nutrient supply in subject-specific TMJ components is superior to other means when a subject-specific diagnosis result is required. However, the TMJ complex anatomy, together with dense blood vessels and surrounding neuron system impedes the direct in vivo measurement in humans without breaking joint function integrity. The continuous development of advanced high-technologies has facilitated the development of many numerous scientific and objective diagnosis tools. Therefore, the objectives of this research are to: 1) build a non-invasive data collection system of TMJ motion, muscular electromyography and bite force and 2) determine the behavioral, functional, and morphological aspects for objective diagnosis of TMJ disorders and understanding the underlying pathology. Our central hypothesis is that TMJ properties of muscle, motion, and shape in patients are sensitive to TMJ disorders and, therefore, can be adapted to enhancing objective diagnosis criteria, functional rehabilitation assessment, therapeutic monitor and understanding the underlying pathology. Aim 1: Determine the muscle activity pattern by calculating EMG parameters for TMJ muscles of mastication. Aim 2: Determine the feature of TMJ kinematics by collecting TMJ motion tracking data and analyzing TMJ motion. Aim 3: Determine the patient-specific TMJ 3D shape signature. The outcome of this study will yield a data collection system for establishing an objective and subject-specific diagnosis and will build a pathway between biomechanics and the pathophysiology