Cardinals starting pitcher Kyle Lohse will undergo surgery on Friday on his right forearm.
Doctors have diagnosed the problem as exertional compartment syndrome.
Dr. Steven Shin, whom Lohse saw for a second opinion on Wednesday, will perform the surgery.
The Cardinals did not project a recovery time for Lohse but athletes in different sports who required similar surgery returned to activity in 6-8 weeks.
Lohse Will Undergo Surgery, Miss Two Months