There has also been considerable attention payed to the contribution of playing surfaces. While it would be logical to assume playing surfaces have decreased injuries over time, many would argue that surfaces such as artificial turf have been key in many serious injuries over the past 10 or so years... specifically in the NFL.
Sure, but some materials are tough on your knies and enkle's.
So you see different injuries.
Top sports always seems to wear out week spots on athletes body (knee, enkle, shoulder or muscle).