A 42-year-old man presents to the emergency department with severe low back pain that began suddenly 24 hours ago after he lifted a heavy pallet at work. The pain radiates down the back of both of his legs. Over the past 12 hours, he has developed a “numb feeling” in his groin and buttocks, especially when sitting. He also reports difficulty starting urination and feels his bladder is not completely empty after trying to void. He has a history of intermittent mechanical low back pain for the last 5 years but has never experienced symptoms like this before. He denies fever, trauma, or a history of cancer. He takes ibuprofen as needed for pain.

His vital signs are unremarkable. His back is atraumatic, but there is tenderness over the spinous processes at L4-L5. Straight leg raise is positive bilaterally at 40 degrees. Neurologic exam as outlined below. Laboratory studies, including a complete blood count and basic metabolic panel, are unremarkable.