A cortisone shot delivers a powerful anti-inflammatory medication directly into a joint, tendon sheath, or soft tissue to reduce swelling and relieve pain. The injection typically contains two components: a corticosteroid that suppresses inflammation over days to weeks, and a local anesthetic that numbs the area immediately. Pain relief can last up to several months, though the shot treats symptoms rather than the underlying condition.
How Cortisone Reduces Pain
Cortisone is a synthetic version of cortisol, a hormone your adrenal glands naturally produce. When injected into an inflamed joint or tissue, it blocks the chemical signals that trigger swelling, redness, and pain. By calming that inflammatory response at the source, the surrounding nerves stop firing pain signals as intensely. This is why cortisone shots work well for conditions driven by inflammation: arthritis, bursitis, carpal tunnel syndrome, and certain types of back pain.
The local anesthetic mixed into the injection provides near-instant numbness, which is why some people feel immediate relief. That wears off within hours. The corticosteroid takes longer to kick in, typically two to three days, because it needs time to suppress the inflammatory cascade in the tissue. Once it does, the relief can persist for weeks or months depending on the condition being treated and how much inflammation is present.
What the First 48 Hours Feel Like
Many people are surprised that a cortisone shot can temporarily make things worse before it gets better. A short-term flare of increased pain, swelling, and irritation is common in the first one to two days after injection. Research on hand, wrist, and shoulder injections puts the rate of post-injection flare at roughly 33 to 35% of patients. The flare can feel similar to a gout attack: sharp, throbbing pain that’s noticeably worse than what you walked in with.
Ice and over-the-counter pain relievers usually manage the flare until it subsides. After those first couple of days, pain and swelling should start to improve. If your pain keeps getting worse beyond 48 hours, or you develop fever or redness spreading from the injection site, that warrants a call to your provider since infection, while extremely rare (about 1 in 40,000 injections), needs prompt treatment.
How Long Relief Lasts
The duration varies widely. Some people get several months of meaningful pain reduction from a single shot. Others notice relief fading after a few weeks. The biggest factors are the severity of the underlying condition, the specific joint or tissue involved, and how much physical stress that area endures in daily life. A cortisone shot in a weight-bearing knee joint, for instance, often wears off faster than one in a shoulder that gets less repetitive loading.
Most providers space injections at least three to four months apart and limit the number you receive in a single joint per year. Repeated injections carry cumulative risks to the surrounding tissue, which is why cortisone works best as a short-term bridge: buying you a window of reduced pain to pursue physical therapy, modify activity, or prepare for a more definitive treatment if needed.
Effectiveness for Knee Osteoarthritis
Cortisone shots are one of the most commonly requested treatments for knee osteoarthritis, but the evidence here is weaker than many people expect. A well-designed two-year study found that patients receiving cortisone injections every three months had no significant difference in pain or function compared to patients receiving saline injections. The most recent Cochrane review, which pooled 27 randomized trials, found only minimal short-term improvement in pain and function over placebo. The single trial rated as having low risk of bias found no benefit at all.
This doesn’t mean cortisone never helps an arthritic knee. Some individuals do get meaningful short-term relief, especially during an acute inflammatory flare. But the data suggests that for ongoing osteoarthritis management, cortisone injections are not a reliable long-term strategy. If your first shot provides good relief that fades, it’s worth discussing other options rather than assuming repeated injections will keep working.
Risks of Repeated Injections
The corticosteroid in these shots can weaken the tissues it contacts over time. Tendons are the main concern: if the medication is injected into the tendon itself rather than the surrounding sheath, it can degrade the tissue and, in rare cases, lead to rupture. This is why providers are careful about needle placement, particularly in areas like the Achilles tendon or rotator cuff where a rupture would be debilitating.
Soft tissue atrophy, where the fat and connective tissue near the injection site thin out, is another possible side effect. It’s estimated to occur in less than 1% of injections and is more likely at superficial sites close to the skin surface. The thinning typically appears one to four months after the shot and resolves on its own over six to 30 months, though it can leave a visible dent or discoloration in the skin during that period. Skin lightening at the injection site is also possible, particularly in people with darker skin tones.
Effects on Blood Sugar
Even though the injection is local, some of the corticosteroid absorbs into your bloodstream. For most people, this causes no noticeable systemic effects. For people with type 2 diabetes, it can cause a significant and sometimes dramatic spike in blood glucose. Studies show that in patients with well-controlled diabetes, blood sugar can peak anywhere from 165 to 500 mg/dL within hours to days after the injection. Average peak levels in research hovered around 300 to 320 mg/dL, roughly double a normal fasting level.
Blood sugar typically returns to baseline within a few days, though in some cases the elevation can persist for up to three weeks. If you have diabetes and are getting a cortisone shot, you’ll want to monitor your glucose more frequently in the days following the injection and have a plan for managing higher-than-usual readings. Extended-release formulations of cortisone appear to cause smaller blood sugar swings compared to standard preparations.
What to Expect During the Procedure
The injection itself takes only a few minutes. Your provider will clean the skin, may apply a numbing spray or cream, and then insert the needle into the target area. You might feel pressure or a brief sting. For deeper joints like the hip, ultrasound guidance is sometimes used to ensure accurate placement. For more accessible joints like the knee or shoulder, providers often inject based on anatomical landmarks alone.
You can typically drive yourself home and return to most activities the same day, though many providers recommend taking it easy on the affected joint for 24 to 48 hours. Avoiding heavy exercise or repetitive stress on the area during that initial window gives the medication time to settle in and reduces the chance of a flare. There’s no special preparation required beforehand, though if you take blood thinners, your provider may adjust the timing or technique.