Measuring dynamic joint function in juvenile idiopathic arthritis. A 10-year old JIA patient wears two splint-fixed electrogoniometers. He is shown in neutral measurement position for active knee movements. The joint-angle over time is captured during active flexion and extension of the knee. Active ROM is defined as the maximum flexion and extension angle out of three cycles. Knee joint torque is calculated using the segment mass of the foot and lower leg and the acceleration at the start of flexion/extension movements.