Soreness of the left arm is considered physiological factors, but also need to consider pathological factors, such as muscle strain, frozen shoulder, cervical spondylosis, rotator cuff injury and frozen shoulder and other reasons. 1. Physiological factors: for example, the arm is in a position for too long, sleeping at night, arm pressure, wind and cold can appear soreness. Symptoms can be alleviated through rest. 2. Muscle strain: Often tired work or lifting heavy objects can cause muscle strain in the arm, which can cause left arm pain. 3. Cervical spondylosis: Osteomalacia, herniated discs compressing the left cervical nerve can cause radiating pain in the left arm, and some of them may have numbness. 4. Rotator cuff injury: The ligament injury of the left shoulder joint can involve the left arm, resulting in soreness and lifting weakness. 5. Frozen shoulder: Frozen shoulder on the left side may be caused by dehydration and adhesion of the soft tissues around the left shoulder joint, which may lead to soreness of the left arm and restriction of the left shoulder joint activities. If the left arm pain does not get better after resting, go to the hospital for examination and treatment to clarify the cause of the disease.