Arthritides of the temporomandibular joint (TMJ) present significant diagnostic and therapeutic challenges. Degenerative joint disease (DJD) of the TMJ is generally classified as a low-inflammatory condition, whereas septic arthritis represents a high-inflammatory process; these entities exhibit distinct biological behavior, clinical presentation, and management requirements. Septic TMJ arthritis is typically associated with marked pain, periauricular swelling, erythema, and impaired mandibular opening, often necessitating urgent intervention. In contrast, degenerative TMJ disease is frequently subclinical, with clinical signs such as discomfort or mild-to-moderate pain occurring in approximately 25% of affected patients. Accurate diagnosis and treatment planning for TMJ arthritides require advanced diagnostic imaging, including computed tomography (CT), cone beam CT (CBCT), and/or magnetic resonance imaging (MRI). This lecture will review the current diagnostic and therapeutic approaches to TMJ arthritides in dogs and cats and introduce emerging technologies, including TMJ arthroscopy and positron emission tomography/computed tomography (PET/CT).

Degenerative TMJ Disease (TMJ Osteoarthritis)
A definitive diagnosis of TMJ osteoarthritis (TMJ-OA) requires correlation of clinical findings with CT-based imaging. Although TMJ-OA is the most common TMJ disorder, it frequently coexists with other TMJ pathologies. Once isolated TMJ-OA is diagnosed, treatment is directed toward pain control and restoration of joint function. Medical management typically includes non-steroidal anti-inflammatory drugs administered for 2–4 weeks, with or without adjunctive opioid analgesia. Temporary “jaw rest” is recommended during this period by avoiding activities associated with excessive mandibular loading. Controlled physical therapy, consisting of guided mandibular opening and closing exercises, is encouraged to maintain joint mobility and prevent stiffness. Dietary modification to soft food is recommended for the initial days, followed by a gradual return to normal mastication. Surgical intervention, such as condylectomy, is reserved for severe, refractory cases characterized by uncontrolled pain or established ankylosis.

Septic Arthritis of the TMJ
Septic arthritis of the TMJ may develop through hematogenous dissemination or by direct extension of infection into the joint. Unlike TMJ-OA, septic TMJ arthritis is a high-inflammatory condition with rapid progression and significant clinical consequences. Disease development depends on pathogen-related factors (bacterial, fungal, or parasitic virulence) as well as host-related immune responses. Clinically, affected dogs commonly exhibit moderate-to-severe periauricular pain, pain on mandibular motion, regional swelling, erythema, and, in some cases, purulent discharge.

Diagnostic Imaging
While physical examination may raise suspicion for septic TMJ arthritis, advanced imaging is required to establish a diagnosis, guide treatment decisions, and aid prognostication. Contrast-enhanced CT is most commonly employed; CBCT may be used in selected cases, and MRI is indicated when soft-tissue or intracapsular pathology is suspected. Conventional skull or dental radiographs are insufficient for assessment of TMJ arthritides. Cytology and Histopathology. Whenever feasible, arthrocentesis or exploratory arthrotomy should be performed to obtain samples for cytology, histopathology, and culture with antimicrobial sensitivity testing. Initiation of targeted antimicrobial therapy based on culture results is strongly associated with improved clinical outcomes.

Surgical Management
Surgical exploration is performed via a lateral approach to access both the dorsal and ventral compartments of the TMJ. Following identification of the joint capsule, a horizontal capsulotomy is performed to expose the joint. The articular disc is carefully mobilized from its dorsal and ventral attachments, permitting inspection of both compartments. Foreign material, if present, is removed, and representative tissue samples are collected prior to initiation of systemic antimicrobial therapy. Each compartment is then lavaged with sterile isotonic saline via indwelling catheters before routine three-layer closure of the surgical site.

References
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