Team principal Eric Boullier has confirmed to Press Association Sport the issue materialised during last month's Belgian Grand Prix.
It is understood to be a throwback from a testing accident at Magny Cours Raikkonen was involved in during his rookie year in 2001 with Sauber.
The current problem, related to a trapped nerve, was so painful after final practice that Raikkonen almost pulled out of qualifying, with Lotus preparing reserve Davide Valsecchi for the drive.
Clearly suffering, Raikkonen could only manage 13th quickest around a 23-corner circuit that is arguably the hardest on the calendar.
"This morning was very bad," said Raikkonen.
"I couldn't really try, so we probably didn't get done what we wanted with the car, but at least we got it on the grid and we'll see what we can do in the race.
"It was good we drove in qualifying in the end, but it was not that nice."
As to whether he will still compete, Raikkonen added: "We will race and see what happens."
Explaining Raikkonen's problems, Boullier said: "Every time he has been flying off a kerb he has been complaining about his back.
"On Friday (in practice) he jumped off a kerb and Red Bull sent one of their physios to help our physio to fix it.
"This morning, when he went out on his first run, the pain returned."
Boullier then joked: "And no, it's not related to any other event because somebody asked me if he got drunk last night and fell off a chair!"
Asked as to whether Raikkonen would take part in the next two races in Korea and Japan next month, Boullier added: "It's too early.
"Let's get through the weekend, he will see his doctor, and we will see how it goes."
At least Romain Grosjean came to the fore, as Boullier had demanded this week in light of Raikkonen's decision to return to Ferrari from next season.
The Frenchman qualified third behind Red Bull's Sebastian Vettel and Nico Rosberg in his Mercedes.
Boullier said: "Since the beginning of July he has been on it in every race, matching the performance of his team-mate, which has been good.
"This weekend we have been watching him to see what he will do, and he has clearly stepped up.
"He has kept building up, and after practice three we knew he could do well. He didn't crack under pressure. He just did it."