A cortisone shot delivers a synthetic version of cortisol, your body’s natural anti-inflammatory hormone, directly into a painful joint or tissue. Instead of traveling through your entire bloodstream like an oral medication, the injection concentrates a high dose right at the source of inflammation, which is why it can provide relief that lasts weeks or months from a single treatment.
What Happens Inside the Joint
When a joint is inflamed, the lining of your blood vessels near the injury becomes sticky. Your immune cells latch onto these sticky surfaces, pile into the surrounding tissue, and release chemicals that cause swelling, heat, and pain. This process is useful after an acute injury, but in conditions like arthritis or tendinitis, it becomes chronic and self-reinforcing.
The corticosteroid in the injection works by entering cells near the injection site and binding to a specific receptor inside them called the glucocorticoid receptor. Once activated, this receptor travels into the cell’s nucleus and changes which genes get turned on or off. The key effect: it dramatically reduces the production of the sticky molecules on blood vessel walls that recruit immune cells to the area. In lab studies, corticosteroids reduced immune cell adhesion to blood vessel walls by roughly fourfold compared to untreated inflamed tissue. Fewer immune cells arriving means less swelling, less chemical irritation of nerve endings, and less pain.
This is also why cortisone doesn’t heal the underlying problem. It suppresses the inflammatory cascade, essentially turning down the volume on your immune response in that specific spot. Once the drug wears off, inflammation can return if the root cause (cartilage wear, repetitive strain, autoimmune activity) is still present.
What the Injection Feels Like
Before the corticosteroid goes in, your provider typically numbs the area with a local anesthetic like lidocaine, injected just under the skin with a very fine needle. The corticosteroid is often mixed with this anesthetic, which serves a dual purpose: it provides immediate (though temporary) pain relief, and it helps the medication spread more evenly through the joint space. The entire procedure takes only a few minutes.
For joints that are difficult to access, like the hip, some providers use ultrasound imaging to guide the needle to the exact right spot. For larger, more accessible joints like the knee or shoulder, the injection is often done by feel using anatomical landmarks.
The most commonly used corticosteroids for injections include triamcinolone, methylprednisolone, dexamethasone, and hydrocortisone. Your provider chooses among these based on the joint being treated and how long they want the effect to last. Some formulations are designed to dissolve slowly, extending the duration of relief.
Timeline: Pain Relief and the Post-Injection Flare
Here’s something that catches people off guard: you may feel worse before you feel better. Cortisone shots commonly cause a short-term flare of increased pain, swelling, and irritation that can last up to two days. This happens because the crystalline structure of the medication itself can irritate the tissue before it dissolves and starts working. Ice and over-the-counter pain relievers can help you get through this window.
After the flare subsides, the anti-inflammatory effect builds over the next several days. Most people notice meaningful improvement within a week. The relief can last up to several months, though the exact duration varies widely depending on the condition being treated and how much underlying damage exists. Someone with mild tendinitis might get months of relief, while someone with advanced arthritis might notice the effect fading sooner.
How Many You Can Safely Get
Cortisone is not something you can keep getting indefinitely. Most providers recommend no more than three injections per year in any single joint, with shots spaced at least 12 weeks apart. The total across all joints is generally capped at six injections per year.
These limits exist because repeated corticosteroid exposure can weaken the tissues it’s meant to help. Over time, frequent injections may thin the cartilage within a joint, weaken nearby tendons, and cause the skin and fat tissue around the injection site to atrophy or lose pigment. The medication can also temporarily raise blood sugar levels, which is especially relevant if you have diabetes. Each individual injection carries relatively low risk, but the cumulative effects of many injections are what providers try to avoid.
Why It Works for Some Conditions Better Than Others
Cortisone shots tend to work best when inflammation is the primary driver of your pain. Conditions like bursitis, inflammatory arthritis flares, frozen shoulder, and plantar fasciitis often respond well because the pain is largely caused by the immune response itself. Remove the inflammation and the pain drops significantly.
They’re less effective when structural damage is the main issue. A torn rotator cuff or bone-on-bone osteoarthritis involves mechanical problems that inflammation suppression can’t fix. In these cases, a cortisone shot may still reduce pain temporarily by calming the secondary inflammation around the damage, but it won’t change the trajectory of the condition. This is why cortisone is often used as one piece of a broader plan that includes physical therapy, activity modification, or in some cases, surgery.
The injection also works better when the medication reaches the right tissue. A shot placed precisely into an inflamed bursa will outperform one that lands in nearby muscle. This is one reason ultrasound-guided injections have become more common for deeper or harder-to-reach structures.