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.