Combined spinal-epidural anesthesia (CSE) is considered safe in lower limb surgeries. We report a case of sudden neurological deterioration in a stable postoperative patient who was given CSE for total knee replacement and low molecular weight heparin in postoperative period. On the 4(th) postoperative day, she developed sudden onset weakness in left lower limb along with bladder incontinence. Magnetic resonance imaging spine revealed a subdural hematoma at L2-L3 level. Immediate laminectomy along with cord decompression was done and patient recovered well except for a persistent foot drop on left side.