After percutaneous endoscopic lumbar discectomy (PELD), postoperative radiating leg pain could persist and become a common problem. This symptom provides important information for use in deciding on performance of reoperation for remnant disc or recurrent disc herniation. Of 225 patients who underwent PELD, 51 patients had persistent radicular pain. Steroid injection to epidural space resulted in pain reduction of at least 50 % in 15 (30.3 %) of these patients. Thirty five cases showed a bad outcome after steroid injection, indicating high sensitivity for detection of a remnant or disc herniation in follow up Magnetic Resonance images (25 cases, 71.4%). Twenty one patients were treated by reoperation. Steroid injection has a diagnostic value with a high sensitivity for mechanical compression of the nerve root as remaining or recurrent disc herniation in MRI for the necessity of a re-operation.