Arthritis of the temporomandibular joint (TMJ) is a long-recognized feature of juvenile idiopathic arthritis (JIA). The consequences of longstanding TMJ inflammation — severe micrognathia and retrognathism — were mentioned in the original description of Sir Frederic Still1. Growth problems are common in JIA, but the extent of growth failure seen in the mandible of children with TMJ arthritis by far exceeds arthritis-related growth complications of other locations. They are caused by unique properties of the mandible: in contrast to what one would assume, the mandible does not grow at the chin. The teeth-bearing body of the mandible undergoes only minimal growth during childhood, while the majority of new bone formation takes place on the mandibular ramus and condyle2. In fact, the majority of mandibular growth originates from chondrocytes immediately adjacent to the TMJ joint space. Because of this close proximity, the inflammatory cytokines in the synovial fluid may have a direct effect on condylar growth very early on in the event of arthritis3. Further, the total growth of the mandible during childhood is considerable, and thus also the potential effect size of disturbed growth of this bone.
Another unique factor of TMJ arthritis in JIA is the absence of clinical signs and symptoms in most patients. In the study of Twilt, et al4, only 12% of patients had TMJ pain; Billiau, et al found 22% with muscle or joint tenderness5, and Argyropoulou, et al found 5%−8% with pain or chewing discomfort6. Also, clinical examination is not able to reveal early signs of active TMJ arthritis, even when performed by skilled examiners; whether they are pediatric rheumatologists or orthodontists, they will reliably find only the signs of …
Address correspondence to Dr. Saurenmann; E-mail: traudel.saurenmann{at}kispi.uzh.ch