Was the context you heard this in regarding a burn situation? I suspect it was.
Burns to certain body parts have a greater impact on the victim over burns to certain other body parts. An example would be the hands. The post healing scars - depending on the degree of the burn - could render the person unable to move his fingers again. On the other hand (no pun intended), a scald to the thigh or back (again depending on the degree), with some grafting could heal nicely and never really impact the victim in the future again mobility-wise. See http://www.revolutionhealth.com/conditions/first-aid-safety/first-aid-treatment/burns/how-serious-burns for a few more details.