"It's just one of those uphill battles he's had," manager Mike Matheny said. "Hopefully we can get him strengthened to where he can get back into baseball shape. The guy can't catch a break here."
Berkman's third stint on the DL this season began Aug. 3, after his surgically repaired right knee gave out on him during an at-bat the night before.
Though Berkman's left knee has given him issues in the past, it had not, until now, been a bother to him this year. Berkman underwent arthroscopic surgery on his left knee in March 2010.
The Cardinals do not know how long the overall rehab process will take Berkman, though general manager John Mozeliak said that he "would speculate that right now [Berkman] is still a couple of weeks away."
Mozeliak also said the Cardinals will likely have Berkman take some Minor League at-bats before rejoining the big league club. Berkman did not go out on a rehab assignment when he returned after a near two-month layoff from right knee surgery.
"All along," Mozeliak said, "we knew those knees were tricky."
Berkman has played in just 28 games this season. Since his rookie season, Berkman has never appeared in fewer than 122 in a year.