The left posterior rib cage can be caused by trauma, costochondritis, intercostal neuralgia, etc. Trauma: traumatic impact or falling and bumping can cause pain, swelling and limitation of movement. 1. Trauma: traumatic impact or fall bump, can cause pain, swelling and activity restriction of the left posterior rib cage, etc., damage to the cutaneous nerve can lead to localized numbness, tightness and so on. 2. Costal chondritis: caused by a variety of reasons, the cartilage at the junction of the sternum and the ribs undergoes inflammatory reaction, and the stimulation of inflammation can cause localized weakness, numbness, pain and other uncomfortable symptoms. 3. Intercostal neuralgia: Intercostal neuropathy caused by degenerative vertebral lesions, tuberculosis, injury, inflammation, tumor, viral infection and other factors can involve the left posterior rib cage, resulting in radiating pain, numbness, and stuffiness from the back along the intercostal space to the chest and abdominal wall, with a semi-annular distribution. When the left posterior ribcage is numb and tight, it is necessary to consult a doctor in a timely manner, under the guidance of a specialist to actively carry out appropriate treatment, which will help to alleviate the uncomfortable symptoms as soon as possible.