Biceps tendon instability. The long head of the biceps tendon is stabilized by the biceps pulley. Damage to the biceps pulley can cause biceps instability and medial displacement of the biceps tendon. On this axial fat-saturated T1 weighted MR arthrographic image, the long head of the biceps tendon is displaced medially (yellow arrow) and is found lying within the subscapularis tendon which presents an increased signal intensity (green arrow).