The long head tendon of the biceps brachii passes through the intertubercular groove of the humerus and enters the anterior part of the subacromial space, ending at the supraglenoid tuberosity of the scapula (Figure 1). The tendon slides passively in the intertubercular groove of the humerus, that is, the tendon slides upward when the shoulder joint is adducted, internally rotated, and extended, and slides downward when it is abducted, externally rotated, and flexed. Tenosynovitis of the long head of the biceps brachii is a lesion in which this part of the tendon is subjected to long-term wear and tear during shoulder joint movement, resulting in degeneration and adhesion, which impairs the sliding function of the tendon. This disease is more common in patients over 40 years old. The main clinical features are pain in the intertubercular groove of the humerus and limited shoulder joint movement. If not treated in time, it can develop into frozen shoulder.