Patterns of compensation of functional deficits of the knee joint in patients with juvenile idiopathic arthritis

OBJECTIVES: Juvenile idiopathic arthritis (JIA) is a group of pathological syndromes of unknown aetiology, observed at the developmental age. Their common feature is sustained chronic arthritis with flares and remissions. Clinical signs and symptoms include joint pain, periarticular tissue oedema or articular exudate, frequently associated with hypertrophy of the synovial membrane. The intra- and extra-articular structural damage impairs the motion range and smoothness. The disease process may involve any joint. The knee joint is the most frequently affected in oligo- and polyarthritis. The aim of the study was to determine a direct correlation between disorders of knee joint function and the change in the range of motion of the ankle and hip joints of both lower extremities, and the so-called indirect impact of these changes on patients’ posture. MATERIAL AND METHODS: The study included 36 JIA patients and 56 healthy controls aged 8–16 years. The evaluation was based on physical examination. RESULTS: The results showed differences in the values of quality and range of motion between patients and controls. In the patient group pes planovalgus was more frequently associated with knee joint dysfunction along with the inherent restriction of dorsal flexion of the foot. Shortening of the iliotibial band, increased outward rotation of the right lower extremity with enlarged joint contour and augmented inward rotation of the contralateral healthy extremity all proved significant. Changes in motion range in the joints below and over the knee were associated with alterations of antero-posterior spine curvatures and vertebral rotation along the long spinal axis. Based on the results, the mechanism of the compensation is outlined. CONCLUSIONS: The observed differences in the range and quality of motion in the ankle, hip and spinal joints between patients and healthy children provide evidence that dysfunction of the knee joint affects the function of the other above-mentioned levels of the motor system.