The shear modulus of the UCL was determined by selecting a region of interest (the solid-line region) by manually tracing the contour of the superficial part of the UCL in the corresponding B-mode image using a custom-designed matlab program. The UCL shear modulus was defined as the median shear modulus in that region. Measurements of the UCL thickness (the length of the right dashed line) and the width of the ulnohumeral joint space (the length of the left dashed line) were illustrated.