No need to add entities for concussion or broken leg. They are by default hard coded to occur when you take damage from any source (to the head or legs respectively).
If you do choose to add infliction entities for those conditions, they will be in addition to the hard coded events, and will not take locational damage into account.
For example, you can make it so a bear has a 50% chance per attack to break your leg, but you can also break your leg by being shot in the leg, or falling from a hight height (by default).
Hops that clarifies things!