There are many reasons why you can’t lift your left shoulder, the common ones are overwork, frozen shoulder, rotator cuff injury, cervical spondylosis, etc. The treatments are also different. Treatments include proper rest, oral medication, triangular towel fixation and other treatments. 1. Overexertion: localized pain in the shoulder after strenuous exercise, which can be recovered after proper rest. 2. Frozen shoulder: when the shoulder is lifted up, it involves the inflamed and adherent tissues, causing pain, which can be treated with local physiotherapy, hot compresses and acupressure. Oral pain medication, such as celecoxib, can also be taken. 3. Rotator cuff injury: When the shoulder is lifted up, the acromion pinches the rotator cuff tissue, causing pain. It is recommended to fix the shoulder joint with a triangle scarf to reduce the activity of the shoulder joint. 4. Cervical spondylosis: mostly due to cervical nerve root compression, caused by shoulder and upper limb pain, numbness or weakness, etc., treatment can be oral nutritional nerve drugs, such as methylcobalamin. There are many other reasons that induce left shoulder pain, such as bone tumor, bone fracture, heart disease, etc. It is recommended to consult a doctor in time to clarify the cause of the disease before treatment.