Serena Williams retires in Madrid

2nd seed Serena Williams retired today in Madrid after she played her first set against Francesca Schiavone. Williams continues to have problems with her knee.

Also retiring was Shahar Peer, who--so it seems--pushed it to hard in Estoril last week, and then went to Madrid and pushed it some more. Peer injured her ankle at the Estoril Open.

Flavia Pennetta retired from her doubles match today with a thigh strain. Yesterday, Kaia Kanepi retired--I no longer recall why. Kanepi is having a bad time of it. Last week in Rome, she double-faulted away a match against Victoria Azarenka in which she had Azarenka quite bewildered and frustrated.