The symptoms of soreness in the left arm are commonly caused by muscle strain in the left arm, periarthritis of the shoulder joint and cervical spondylosis, as follows: 1.Muscle strain in the left arm, prolonged fixed posture or excessive weight bearing, resulting in muscle strain in the left upper limb, will manifest as soreness and swelling of the left arm, accompanied by a feeling of weakness. Cervical spondylosis, which is mainly related to the limitation of shoulder joint movement and nerve radiology, can gradually relieve the symptoms of left arm pain or even disappear completely through manual release treatment as well as cervical traction and braking treatment. Early diagnosis and treatment can help to relieve the symptoms of left arm pain. If treatment is delayed, the soreness in the left arm will be aggravated, and it will lead to muscle atrophy and weakness in the left arm, so if soreness occurs in the left arm, it should be taken seriously and promptly consulted.