Temporomandibular joint disorders is a common condition, Intra-articular causes of TMD include internal joint derangement, osteoarthritis, capsular inflammation, hypermobility and traumatic injury. The most frequent cause of TMJ dysfunction is internal derangement which refers to an alteration in the normal pathways of motion of the TMJ that largely involves the function of the articular disc, therefore, these alterations have been also referred to as disc derangement , signs of which appear in up to 60-70% of the population. The peak incidence is seen in adults aged 20-40 years. Women are at least four times as likely to suffer from the disorder .~Magnetic resonance imaging (MRI) has provided a noninvasive accurate method of assessing the TMJ without associated radiation risks ,its ability to directly visualize the disc and accurately determine the position of the disc with respect to the condyle of the mandible and eminence of the temporal bone. The examination, however, takes 20 to 45 minutes on average to perform depending on the scanner and protocol, and patients have difficulty keeping still and having their mouths open for extended periods of time, especially if they are experiencing pain. In addition, the examination is costly and access is still limited in many centers. Many patients also experience claustrophobia and are unable to complete or even undergo the examination .~Ultrasound is relatively inexpensive, is readily accessible, and can be performed in most outpatient facilities; studies take only an average of 10 to 15 minutes in total, and it is without any known risks. In addition, US provides the opportunity to converse with patients and identify the exact locations of pain, while the probe can be used as a palpable tool for real-time identification of crepitus, clicking, motion, and snapping sensations.~The following US applications were described: Joint effusion, Internal derangement and disc displacement, mainly anterior with and without reduction, Joint function basing on condylar translation range, TMJ dislocation, Guidance in fine-needle aspiration cytology (FNAC), Guidance for TMJ arthrocentesis and Guidance in TMJ injections, e.g., with steroids , Blood .
Evaluation of US efficiency in assessment of the tempromandibular joint disorders in comparison with MRI as the gold standard for technique validation and evaluation of efficiency of therapeutic intra articular injection under sonographic guidance .