Pulmonary Embolism Forces Serena Williams Into Emergency Treatment

Tennis star Serena Williams, out of action since last July, underwent emergency treament on Monday to treat a hematoma, according to People Magazine.

Williams, 29, suffered a pulmonary embolism last week, a blood clot in the lungs that caused the hematoma to form. She is being treated in a Los Angeles hospital, according to the report.

The pulmonary embolism was discovered when Williams was undergoing routine doctors' appointments for her injured foot.

All Williams had to say regarding the emergency treatment came late Tuesday night, when Williams tweeted, "Tough day…."