A 77-year-old female, followed by pain management, presented with 6 months of proximal left lower extremity pain, weakness, and numbness. The 6-month old MR demonstrated significant lumbar stenosis L2-S1, and was interpreted as showing a large left L2-L3 disc herniation with marked inferior migration to the left L3 mid-pedicular level. Two months prior to presentation, she had undergone two epidural steroid injections. When she was finally seen by neurosurgery, she had significant left iliopsoas/quadriceps weakness (2/5), absent lower extremity reflexes, and profound pin loss in the left L2-L3 distrubutions. The follow-up MR and new CT studies were similarly interpreted as showing L2- S1 stenosis and a left-sided L2-L3 disc. However, when she underwent a L2-S1 laminectomy, the left L2-L3 lesion proved to be a massive synovial cyst [, ]. Postoperatively, the patient’s symptoms immediately resolved, and she remained neurologically intact 6 months later.