The pain in the tendon when lifting the left arm may be caused by the following reasons: 1. It may be caused by a shoulder joint related pathology, such as rotator cuff injury of the shoulder joint or frozen shoulder. The former is caused by trauma to the shoulder joint or overexertion, causing damage to the internal ligaments of the shoulder joint, which in turn causes the above symptoms. The latter is often caused by cold or trauma, resulting in aseptic inflammation of the shoulder joint, followed by fibrinous exudation, which causes pain and limited movement of the shoulder joint. 2, It may be caused by a strain of the muscles or tendons of the upper extremity, such as a strain of the deltoid or forearm extensor muscles, which can cause pain when lifting the affected limb. 3, It may be caused by This condition is often caused by trauma or strain to the forearm, resulting in aseptic inflammation or even injury to the tendon stop at the lateral epicondyle of the humerus, which can lead to pain when extending the arm. 4. These areas.