The severity of lesions in the temporomandibular joint (TMJ) area and their association with age at onset, the various forms of juvenile rheumatoid arthritis (JRA), and certain serologic tests for rheumatoid factor (RF), antinuclear antibodies (ANA), and human leukocyte antigen (HLA)‐B27 were determined in 15‐yr‐old children. The series comprised 121 JRA children, 78 girls and 43 boys, in whom an analysis had recently been made of the relation of TMJ lesions to jaw movement and occlusal status. The mean age at onset was 7.3 yr, the girls contracting JRA earlier than the boys. Also, the girls with lesions in the TMJ area were significantly younger than those with no lesions. TMJ abnormalities were found in 50% of cases with a pauciarticular or systemic onset, but in 72% of those representing the polyarticular subtype. Flattened condyles and grave lesions were equally represented in all subgroups and in both sexes. A crossover from onset type to present diagnosis was found in 30% of the cases, mostly from pauciarticular to polyarthritis, which also increased the risk of TMJ lesions from 50 to 60%. RF, ANA, or HLA‐B27 alone did not seem to be associated with a risk of TMJ abnormalities. Maximal opening capacity is more restricted in patients with early onset or a polyarticular mode of JRA. Since the TMJ is affected in more than half of JRA children, regular measurements of maximal movements of the mandible or roentgenologic examinations of the TMJ are essential for their optimal treatment.

– The purpose was to determine the number and severity of lesions in the temporomandibular area and their association with occlusal status and mandibular movements, in 15‐yr‐old children afflicted with juvenile rheumatoid arthritis (JRA). The series comprised 121 JRA children, 78 girls and 43 boys, and a control group of 104 schoolchildren, 70 girls and 34 boys, taken for clinical examination. Of the JRA children, 55% had roentgenologically detectable lesions in the TMJ area. Lesions were found in 60% of the girls and in 42% of the boys, the ratio thus being 3:2. The largest group had grave lesions (48%), the second largest displayed flattening of the condyle (43%) and the smallest a flattened condyle with a minor lesion (9%). There were more bilateral lesions in the children with the severest lesions. Tendencies for Class II malocclusion, small vertical overbite and open bite were visible in the JRA children. Reduced maximal opening capacity, maximal protrusion, lateral movements of the mandible and pain in the TMJ area proved to be reliable signs predicting temporomandibular joint involvement in JRA children. Maximal mouth opening capacity was significantly restricted in the patients showing condylar lesions as compared with patients having no lesions or with controls. JRA children should be divided according to sex and the severity of the lesions. The JRA children without TMJ lesions had normal values for mandibular movements and were thus comparable to healthy children.