A LESI, or lumbar epidural steroid injection, is a pain-relief procedure where a doctor injects an anti-inflammatory steroid into the space surrounding the spinal nerves in your lower back. The goal is to reduce inflammation around compressed or irritated nerve roots, easing pain that radiates from the lower spine down into the buttocks or legs. It’s one of the most common treatments for sciatica and other forms of nerve-related back pain, and it typically provides meaningful relief for about three months.
Why It’s Used
A LESI targets a specific type of pain called radicular pain, which is pain that travels along the path of an irritated spinal nerve. The most familiar example is sciatica, where a pinched nerve in the lower back sends shooting pain, numbness, or weakness down one leg. This nerve irritation usually comes from one of a few underlying problems.
Herniated discs are the most common cause. The soft center of a spinal disc pushes through its tough outer layer and presses against a nearby nerve root. Degenerative disc disease, where discs gradually break down and the space between vertebrae narrows, can produce similar compression. Spinal stenosis, a narrowing of the spinal canal itself, is another frequent reason doctors recommend a LESI. This narrowing is often caused by arthritis in the spinal joints or by disc problems.
Beyond these three main conditions, a LESI may also be used for bone spurs pressing on nerve roots, pain that lingers after spinal surgery, compression fractures with nerve involvement, or conditions like spondylolisthesis where one vertebra slips forward over another.
How It Reduces Pain
When a nerve root is compressed, the surrounding tissue launches a strong inflammatory response. Your body releases chemical signals called cytokines and chemokines that amplify pain, sometimes even without ongoing mechanical pressure on the nerve. A LESI delivers a corticosteroid directly to this inflamed area, calming the inflammatory reaction at its source. By dialing down inflammation, the injection reduces swelling around the nerve root, which relieves pressure and pain.
The injection also typically includes a local anesthetic, which can provide immediate but temporary numbness. The steroid itself takes longer to kick in: most people notice improvement within one to three days, though it can take up to a week to feel the full benefit.
How Well It Works
Short-term results are generally strong. Within four to 12 weeks of the injection, most patients report meaningful pain relief and better physical function. The most targeted version of the procedure, called a transforaminal injection (where the needle is guided to a specific nerve root), has a success rate of 70 to 90% for short-term relief. Other approaches, like interlaminar or caudal injections, show short-term success in roughly 50 to 75% of patients.
Longer-term results are more variable. In one study, about 83% of patients treated with transforaminal injections maintained pain relief and functional improvement at six months. Another found that 70% of patients had relief after a single injection, but only 44% still felt that relief at 16 weeks, and 59% needed repeat injections. For patients with spinal stenosis specifically, one study found that nearly 90% achieved at least a 50% reduction in pain after three months.
Not everyone responds equally. Around 17% of patients in one study ultimately needed surgery or additional treatment, highlighting that outcomes depend on the specific cause and severity of the nerve compression. Patients with disc herniations tend to respond better than those with foraminal stenosis, where only about 34% reported improved outcomes at 12 months.
What the Procedure Feels Like
The procedure is done on an outpatient basis, meaning you go home the same day. You’ll typically lie face down, and the doctor uses imaging guidance (usually fluoroscopy, a type of live X-ray) to place the needle precisely in the epidural space near the affected nerve root. The injection itself takes only a few minutes. You may feel pressure or a brief sting, and some people experience a temporary increase in their usual pain as the fluid enters the epidural space.
Afterward, you’ll be monitored briefly before being sent home. Some numbness or weakness in your legs is normal and temporary, especially from the anesthetic component.
Recovery and Aftercare
Recovery is quick, but the first 24 to 48 hours come with some specific restrictions. You can resume normal activities 24 hours after the procedure, but on the day of the injection, avoid driving, operating heavy machinery or power tools, and making important decisions or signing documents.
For the first 48 hours, don’t lift anything heavier than 20 pounds without help, and avoid swimming, bathing, or soaking the injection site in water. Get up slowly when moving from lying or sitting positions, and have a responsible adult stay with you overnight in case you experience leg numbness. Gentle stretching is encouraged because it helps your body absorb the injected medication. Applying a cool compress (not ice) to the injection site for 20 minutes on and 20 minutes off can ease any soreness at the needle site.
Risks and Side Effects
Common side effects are generally mild: temporary soreness at the injection site, a brief increase in pain, or a slight rise in blood sugar for people with diabetes. Some people experience a facial flushing or mild headache in the days following the injection.
Serious complications are rare but real. The FDA has issued a warning that epidural corticosteroid injections can, in uncommon cases, cause loss of vision, stroke, paralysis, seizures, or death. These events are linked to damage to blood vessels or the spinal cord during the injection. If you experience any unusual symptoms afterward, like sudden vision changes, tingling in your arms or legs, weakness or numbness on one side of your body, a severe headache, or dizziness, that warrants emergency medical attention.
Because repeated steroid exposure carries its own risks (including weakening of nearby bones and soft tissue), doctors generally limit how many injections you receive in a given year. The exact number varies by practice, but most providers cap it at three to four injections per 12-month period.
How Long Relief Lasts
For most patients, a single LESI provides significant pain relief for about three months. Some people experience longer-lasting benefits, while others find relief fading within a few weeks. When the first injection works well but the pain eventually returns, repeat injections are a common next step. The goal is often to create a window of reduced pain that allows you to engage more fully in physical therapy and rehabilitation, which can address the underlying problem and reduce the need for further injections.