To find an objective measure of hip joint effusion with ultrasound (US) in patients with juvenile rheumatoid arthritis (JRA).
The hip joints of 24 children with JRA were evaluated with US. All patients were negative for rheumatoid factor and antinuclear antibodies. Patients with unilateral or bilateral hip pain, swelling, or limitation of range of motion were included. In each hip, the distance from the femoral neck to joint capsule was measured. Values were compared to measurements in a control group of 24 children with no history of hip joint or rheumatic disease. Statistically significant differences between the 2 groups were analyzed by t test. Two standard deviations above the control group mean was used as the standard for an effusion.
There was a statistically significant difference in US joint space between the children with JRA and the control subjects (p < 0.001). The mean in the control group was 0.43 cm and the mean in the JRA group was 0.60 cm. A distance of 0.59 cm from femoral neck to joint capsule was determined to be consistent with an effusion. Using this standard, 71% of the children with JRA had effusion in at least one hip, and 25% had effusion bilaterally. No control subjects had measurements above this level.
Ultrasonography is effective in the evaluation of hip joint involvement in patients with JRA, and may be useful in facilitating the diagnosis, classification, and followup of this illness.