Lohse, who experienced soreness in the arm in his last start on Saturday, will have a fascial release surgery in Los Angeles to alleviate the condition that has plagued him since last season. Dr. Steven Shin will perform the surgery, and Lohse's expected return is not known.
He was placed on the 15-day disabled list, retroactive to May 23.
The condition is known as exertional compartment syndrome, and only after a recent visit to the Kerlan-Jobe Orthopedic Clinic in Anaheim did Lohse receive that diagnosis.
"That explains a lot of things that have been going on with me, and it's good to find out what it is, from my side," Lohse said. "Now we know what it is, and now we just need to figure out how we're going to treat it."
Lohse also explained that there is no precedent of a Major League pitcher having the condition, so the recovery time is unknown, and that even a role change to shorter stints out of the bullpen could cause further damage.
"I don't know if [a role change] is an option right now," Lohse said. "My understanding is that it can continue to cut off blood supply to your muscle there, you're going to have the possibility of damaging nerves and blood vessels. That's more serious than even what I've got going on now."
The Cardinals purchased the contract of right-hander Fernando Salas from Triple-A Memphis to take Lohse's spot on the roster.
Tim Powers is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.