The left shoulder may be sore and numb for the following reasons: first, myofasciitis, myofasciitis patients often have pain on the inside of the scapula as the first symptom, which can radiate to the ipsilateral shoulder and the ipsilateral upper limb, with symptoms of soreness and weakness, especially at night when sleeping under pressure and cold, when tired, shoulder soreness and numbness is very significant, this time to carry out physical examination and related tests to exclude other diseases for diagnosis; Second, cervical spondylosis, when cervical spondylosis compresses the nerve roots, the symptoms of soreness and numbness in the shoulders can also appear, so it is necessary to conduct early physical examination and cervical spine X-ray, CT, and MRI examinations for early diagnosis and treatment.