In his last bullpen session, Penny felt something and the club opted to push him to Monday's series opener against the Reds.
"He has been throwing the ball well, but the fact that he was stiff threw up a red flag for us," manager Joe Torre said. "But after the doctor examined him, that stabilized our confidence and showed he had arm strength."
Penny, who is 5-4 with a 5.09 ERA in nine starts for Los Angeles this season, has allowed 15 runs over his last two outings while allowing 19 hits and walking four.
Penny has averaged 190 innings and 32 starts over his three seasons with the Dodgers, but he also has made four trips to the disabled list in his career. In 2004 and '05, Penny spent time on the DL with a nerve injury in his right biceps, and in 2002, he had inflammation in the biceps. Penny also suffered an impingement in his right shoulder in 2000.
Lowe, who will be going on three days' rest, is 2-3 with a 4.52 ERA in nine starts. Over his last three starts, Lowe has also struggled, allowing 15 runs, 20 hits and nine walks.
Mike Scarr is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.