The most common cause of left back pain is lumbar back fasciitis or frozen shoulder, the details are as follows: 1. Lumbar back fasciitis: It may be due to prolonged ambulatory work, frequent bending over to do housework, and playing with the phone with the head down, causing the lumbar back fascia to be in a high tension state for a long time, which can easily cause strain on the lumbar back fascia, thus manifesting as back pain; 2. Frozen shoulder: When frozen shoulder occurs, it can appear as shoulder joint Peripheral pain, also including pain in the scapular region, that is, pain in the back of the left scapular region. When periarthritis occurs, local hot compresses should be applied, and anti-inflammatory and pain-relieving drugs should be actively used to relieve the pain symptoms, while functional training of the shoulder joint should be carried out, so that adhesions of the shoulder joint can be prevented to improve the function.