Joe
Thanks for your question. If you watch the youtube video of the hit that Brett took, you'll can appreciate that the full impact of his fall was on his entire Right arm.
http://www.youtube.com/watch?v=OFkeMmROoV0
In addition to sustaining a sternoclavicular sprain, I suspect that he had a severe contusion to the arm and forearm. In this case bleeding occured and caused a large
ecchymosis).
ec·chy·mo·sis noun \ˌek-ə-ˈmō-səs\plural ec·chy·mo·ses \-ˌsēz\
Definition of ECCHYMOSIS
:
the escape of blood into the tissues from ruptured blood vessels marked by a livid black-and-blue or purple spot or area; also : the discoloration so caused —ec·chy·mot·ic \-ˈmät-ik\ adjective
So---the purple discoloration was not caused by the shoulder injury, but by a contusion to the arm and hand. Blood spreads along the fatty tissue planes where there is little resistance, much like the way a paper towel wicks up spilled grape juice on a countertop.