Left armpit and left arm pain in the elderly can be caused by trauma, frozen shoulder, lymphadenitis, cervical spondylosis and other factors. 1. Trauma: the left arm is hit by external force or over-expansion of the upper arm, resulting in the armpit being pulled, which can cause bone and soft tissue injury in the left arm and left armpit, resulting in pain symptoms. 2. Frozen shoulder: Inflammation around the left shoulder joint may cause pain and discomfort in the neck, shoulder and its surrounding areas, and the pain may radiate to the scapular region of the back, the axilla of the same side and the inner side of the upper arm, which may lead to pain in the left armpit and the left arm. 3. Lymphadenitis: After the germs invade from the axillary skin, they can enter the lymphatic vessels through the lymphatic space of the tissues and cause inflammation of the axillary lymph nodes, which can be manifested as pain in the left armpit and the left arm, and the enlarged lymph nodes can be touched locally, accompanied by fever and other manifestations. 4. Cervical spondylosis: After cervical spondylosis compresses the nerves, it can lead to pain in the innervated areas such as the left armpit and left arm, and can be accompanied by numbness, weakness and other discomforts. When the left armpit and left arm pain in the elderly, should promptly consult a doctor, under the guidance of specialists to actively carry out appropriate treatment, help early relief of pain and other discomfort symptoms.