Left side rib pain when pressed may be caused by external injury, and may also be related to acute costochondritis, intercostal neuritis and other diseases. 1. External injuries: due to bumping and impact injuries, it may lead to contusion, dislocation or even fracture of ribs, resulting in pain on the left side of the ribs when pressed. 2. Acute costochondritis: it may be related to viral infection, chronic strain of thoracic and rib joint ligaments or endocrine abnormality, causing cartilage nutritional disorders, which may be manifested as pressure pain on the left side of the ribs when pressed. 3. Intercostal neuritis: mostly related to viral infection, nerve compression, etc., manifested as strip-like pain along the ribs travel area, pain is obvious when pressing. There may be other reasons for the left side rib pain when pressed, so you should consult a doctor in time to clarify the specific reasons and carry out appropriate treatment if necessary.