Intra-articular and skin surface temperature of the temporomandibular joint in patients with rheumatoid arthritis.

Intra-articular and skin surface temperatures of the temporomandibular joint (TMJ) were investigated in 34 patients with rheumatoid arthritis (RA). History was taken, and a clinical examination of the stomatognathic system was performed. The intra-articular temperature measurement was made with a thermocouple inserted through a needle, and the skin surface measurement was made with a thermocouple lateral to the condylar pole. The intra-articular temperature was lower for 37% and higher for 30% of the patients, whereas skin surface temperature was lower for 18% and higher for 6%, compared with normal individuals. Intra-articular and skin surface temperatures were positively correlated, and the average difference between skin surface and intra-articular temperatures was 1.6 degrees C. The intra-articular temperature was most strongly and positively correlated to the number of joint regions affected by RA and negatively correlated to the number of tender masticatory muscles, whereas skin surface temperature was most strongly and positively correlated to room temperature and negatively correlated to the number of tender masticatory muscles. These results indicate that pain and tenderness of masticatory muscles in RA are associated with hypothermia of the TMJ.