Rib or breastbone fractures
Similarly, ribs can be bruised or occasionally fractured. These produce pain on breathing not unlike the popped rib cartilage, but the casualty may indicate pain further back around the ribs into the bony portion. There may or may not be painful movement in the ribs on gentle pressure and it can be impossible to tell on field whether ribs are just bruised or fractured (and similarly impossible in hospital). It is safest to judge decisions on whether the player can breathe normally and whether they think they are too sore to take contact again on that area.
A fractured rib can cause bleeding around the underlying lung (haemothorax) or even puncture it due to a sharp bony edge causing it to collapse down (pneumothorax). Hence, suspected fractured ribs need to be treated with respect, the player removed from the field and not left alone until reviewed by medical staff.
The lower ribs also protect other organs of the body- the liver on the right, the spleen on the left and, to a small degree, the kidneys at the back. Consequently, injuries to the ribs can also mean injuries to any of these organs also.
Breastbone injuries (sternum) are different in that the heart sits directly underneath the injured area. Those who sustain a painful injury to the sternum and who describe a painful click need assessing in hospital.