BERLIN (AP) _ An arm injury forced Serena Williams out of her quarterfinal match against Arantxa Sanchez-Vicario at the German Open today.

Sanchez-Vicario took the first set 6-3 and was up 3-2 in the second when Williams quit.

Williams appeared to have suffered a muscle problem in her right arm. She had the arm treated and taped during several changeovers but was clearly unable to continue. She was seeded sixth..

Ruxandra Dragomir of Romania also advanced to the semifinals of the $1 million clay-court tournament by upsetting eighth-seeded Patty Schnyder of Switzerland 3-6, 6-1, 6-1.