You’ll lie on your side with your knees drawn close to your chest, or you'll sit, with your arms and head on a table. After doctors cleanse and cover the skin around your lower back, you’ll get medicine to numb that area. Your doctor will put a long, thin hollow needle in your lower back between two bones in your lower spine and into the space filled with cerebrospinal fluid (CSF). He’ll take 1-2 tablespoons of fluid and remove the needle. The procedure doesn’t touch your spinal cord.