Muscle strength and thickness were studied in children with juvenile chronic arthritis (JCA) to evaluate their muscle function.
We studied voluntary isometric, isokinetic, and nonvoluntary isometric muscle strength, as well as muscle thickness, in 20 children with JCA. Thickness of the quadriceps muscle was measured by ultrasound. Results were compared with reference values for healthy children and a matched control group.
Isometric muscle strength in knee extensors, elbow flexors, and wrist dorsiflexors was reduced in children with JCA. In muscles near an inflamed joint, the strength was 45-65% of expected value. In muscles without adjacent arthritis, the strength was slightly decreased (80-90% of expected value). Isometric and isokinetic strength in ankle dorsiflexors was reduced only in children with ankle arthritis. Nonvoluntary muscle strength in thumb adductors during electrical stimulation of the ulnar nerve was reduced in children with arthritis in the hand. Thickness of the quadriceps muscle was reduced both in children with and without knee arthritis (75 and 90% of expected).
Children with JCA have reduced muscle strength and thickness, which is most pronounced in muscles near an inflamed joint.