The Cubs put Putnam on the disabled list on Wednesday, and he underwent an MRI later that day.
"I have not talked to Dr. (Stephen) Gryzlo (the team orthopedic surgeon) yet about the test," Putnam told ESPNChicago.com on Thursday.
The Cubs knew that Putnam had the bone spur, and the MRI was given to make sure there is no other damage in the arm, according to a team source.
Putnam was 0-0 with an 18.90 ERA in five relief appearances. The Cubs recalled Brooks Raley from Triple-A Iowa to take his spot on the roster.