Contusions are surgical injuries—other than fractures or wounds proper—in which the skin is not broken. The producing force is usually blunt. Most wounds are more or less complicated by contusion. It may involve the skin alone, or any of the subcutaneous structures as muscles, nerves, viscus or bone. There is always present some degree of vascular rupture. A contusion may be defined as a hidden wound modified by the nature of its surrounding parts. Simple contusions are more apt to be found where there is a plentiful supply of fat or muscle interposed between the bony frame-work and the vulnerating force, upon the character of which the nature of the injury largely depends.
—The pain which follows is not always proportionate to the injury. There is usually some degree of numbness, followed by marked aching or throbbing during the inflammatory stage, accompanied to a greater or less degree
LUCKEY JE. SUBCUTANEOUS INJURIES OF SOFT PARTS.. JAMA. 1898;XXX(2):57-62. doi:10.1001/jama.1898.72440540005002a