From Blabbermouth:
ZAKK WYLDE Treated At Hospital For Blood Clot - Aug. 22, 2009
Zakk Wylde (BLACK LABEL SOCIETY, OZZY OSBOURNE) was apparently taken to a local hospital emergency room following BLACK LABEL SOCIETY's August 19, 2009 concert in Missoula, Montana in order to receive treatment for a blood clot (see photo below). According to a posting on Zakk's official Twitter account, he was headed back to the hospital today to receive further medical attention for the same condition. No further details are currently available.

(wrong smiley choice for this thread...ooops)