Ultrasound-guided temporomandibular joint (TMJ) injection is useful in the diagnosis and management of a variety of painful disorders of the TMJ, including arthritis, myofascial pain, and TMJ disk dysfunction (Fig. 14.1; Table 14.1). This technique can be utilized to inject autologous blood and platelet-rich plasma into the joint when treating joint hypermobility and recurrent joint dislocation as well as to inject viscosupplementation agents such as hyaluronic acid derivatives. Recently, the use of botulinum toxin injections to treat TMJ disk dysfunction has been advocated when more conservative treatment options have failed to provide palliation of the patient’s pain and joint dysfunction. Internal derangement of the intra-articular disk may manifest itself clinically as popping, clicking, catching, or locking of the joint (see Fig. 14.1). Dental malocclusion or bruxism may exacerbate these problems. Patients suffering from TMJ pain may also complain of otalgia and headache, which is often worse in the morning in contradistinction to tension-type headache that often worsens as the day progresses. Evaluation of TMJ pain must also include a targeted evaluation of the associated structures, including the masseter and temporalis muscles (Fig. 14.2).

The TMJ is a ginglymoarthrodial joint, meaning that it is a two-compartment joint (Fig. 14.3). Like the sternoclavicular joint, the TMJ has two synovial-lined compartments divided by a fibroelastic cartilaginous articular disk (Fig. 14.4). When the mouth initially opens, the movement occurs primarily in the lower compartment of the joint as the condylar head rotates. As the mouth opens more widely, the upper compartment begins to function by allowing a secondary forward and downward gliding motion known as translation. The intraarticular disk changes the position during mouth opening, and internal derangement of this disk may result in pain and TMJ dysfunction (Fig. 14.5). It should be noted that extracapsular causes of TMJ pain are much more common than internal disk derangement. The sensory innervation of the TMJ is provided by branches of the mandibular nerve. The muscles involved in TMJ dysfunction include the temporalis, masseter, and external pterygoid and internal pterygoid muscles, which are innervated by motor fibers of the mandibular nerve, and may also include the trapezius and sternocleidomastoid (Fig. 14.6). Trigger points may be identified when palpating these muscles. The articular joint space between the mandibular condyle and the glenoid fossa of the zygoma is easily accessible for injection utilizing the ultrasound-guided technique described below.

Ultrasound-guided TMJ injection is a straightforward technique if attention is paid to the clinically relevant anatomy. To perform ultrasound-guided TMJ injection, the patient is placed in the supine position with the cervical spine in the neutral position. The TMJ is identified by drawing an imaginary line between the tragus of the ear and the ala of the nose (Camper line) (Fig. 14.7). The joint is then identified by gentle palpation along this line while the patient open and closes his or her mouth (Fig. 14.8). Once the TMJ is identified, the patient is asked to close his or her mouth, but not to clench their teeth. The skin overlying the TMJ is prepped with antiseptic solution, and a high-frequency linear transducer is placed directly over the joint in a transverse position (Fig. 14.9). The TMJ should be readily apparent with the acoustic shadow of the curved bony mandibular condyle and mandibular neck just below it (Fig. 14.10). In order to most clearly see the joint space, the ultrasound transducer may need to be tilted slightly in a cephalad or caudad direction to align the ultrasound beam in a true perpendicular plane relative to the joint.