How long does it take for a cortisone shot in the knee to work?

Most people feel meaningful pain relief from a cortisone shot in the knee within two to five days, though some notice improvement in as little as 24 hours. The catch is that the first day or two can actually feel worse before things improve, and how long the relief lasts varies enormously depending on the severity of arthritis, body weight, and even how precisely the needle was placed. The timeline is more complicated than a single number, and knowing what to expect at each stage helps you judge whether your injection is working normally.

The First Few Days After Injection

Corticosteroids suppress inflammation by dialing down the immune signals that cause swelling and pain in the joint lining. That process is not instantaneous. The drug needs time to bind to receptors inside cells and change gene activity related to inflammation, so the full anti-inflammatory effect builds over roughly 48 to 72 hours. During this window, the joint may actually feel more irritated than it did before the shot.

A prospective study tracking 140 patients who received musculoskeletal corticosteroid injections found that about one in five experienced a pain flare after the procedure.¹ These flares are usually mild and resolve within a day or two. They are caused by the needle itself irritating the joint tissue, the crystalline steroid particles provoking a brief inflammatory reaction, or both. If your knee feels sorer the evening after the shot, that is common and not a sign the injection failed.

Many providers mix a local anesthetic like lidocaine or bupivacaine with the steroid. This gives you a few hours of near-complete numbness right after the injection, which can be misleading. When the anesthetic wears off, the underlying pain returns and may even feel amplified before the steroid kicks in. Think of it as a gap period: the anesthetic has faded, but the cortisone has not yet reached full effect.

When Pain Relief Peaks and How Long It Lasts

For knee osteoarthritis, cortisone injections tend to deliver their strongest relief somewhere around one to three weeks after the shot. Most research frames the benefit as primarily short-term.² In practical terms, that means the window of good relief often runs from roughly one week to about six weeks post-injection, with gradual decline after that. By three months, many patients report that their pain has returned to somewhere near pre-injection levels, though some get longer stretches.

The steroid formulation matters for the timeline. Standard immediate-release triamcinolone acetonide floods the joint quickly, reaching peak concentrations in the blood within hours.³ Extended-release formulations use microsphere technology to release the drug more slowly within the joint, producing lower blood levels of steroid overall. In some patients, particularly those with diabetes who need to worry about blood sugar spikes, the extended-release version may offer a meaningful advantage because it keeps more of the drug local and less of it circulating systemically.

If you feel no improvement at all by the two-week mark, the injection may not have landed accurately inside the joint space, or your arthritis may be too advanced for corticosteroids to make a noticeable dent. At that point, it is worth following up with your provider rather than assuming you need more time.

Why Results Differ So Much From Person to Person

Two people with “knee arthritis” can get the same injection on the same day and have wildly different outcomes. The biggest predictors are arthritis severity and body weight. In one study, patients with milder arthritis (lower radiographic grades) showed significant improvement in pain and function scores at every follow-up through three months. Meanwhile, obese patients with more advanced arthritis had worse scores at every time point, including baseline, six weeks, and three months.⁴ In plain terms, if your arthritis is still relatively mild, a cortisone shot is more likely to work well and work longer. If the joint is severely worn and you carry extra weight, you are less likely to get a dramatic or lasting response.

Injection accuracy is another underappreciated factor. It might seem obvious that the needle needs to get inside the joint, but it does not always. A systematic review of randomized controlled trials found that ultrasound-guided knee injections were more accurate than injections placed by feel alone in every study examined, with blind injections showing inconsistent accuracy rates that varied depending on the approach angle used.⁵ A separate randomized controlled trial found that about a third of injections guided by physical landmarks alone missed the target, and that accurate injections led to greater improvement in joint function at six weeks compared with inaccurate ones.⁶ If your shot did not seem to help, ask your provider whether ultrasound guidance is available for the next attempt.

What to Do (and Not Do) Right After the Shot

There is an old debate about whether you should rest the knee after a cortisone injection or go about your day normally. The evidence leans toward at least some rest. A randomized controlled trial comparing strict 24-hour bed rest to normal activity after knee steroid injections found that the rest group had better pain scores, less stiffness, and improved walking times that persisted all the way out to six months.⁷ That study used strict inpatient bed rest, which is not realistic for most people getting an outpatient injection. But the underlying principle holds: taking it easy for a day or two after the shot likely helps the steroid settle into the joint tissue rather than getting dispersed by movement.

Current expert recommendations for high-level athletes suggest one to two days of rest followed by a progressive increase in activity.⁸ For everyday patients, something similar makes sense: avoid heavy exercise, long walks, or standing on your feet all day for at least 24 to 48 hours. Light movement around the house is fine. This rest period also helps minimize systemic absorption of the steroid, which reduces side effects like blood sugar spikes and facial flushing.

Blood Sugar Spikes and Other Side Effects

If you have diabetes, cortisone shots deserve special attention. The steroid is meant to stay in the joint, but some always leaks into the bloodstream. That systemic steroid raises blood glucose, sometimes substantially. A study of diabetic patients receiving shoulder injections found that those with well-controlled diabetes (hemoglobin A1c below 7%) saw an average blood sugar rise of about 38 mg/dL, while those with poorly controlled diabetes saw a rise of about 98 mg/dL.⁹ In the well-controlled group, glucose returned to near-normal around eight days post-injection, while it stayed elevated longer in the poorly controlled group. Insulin-dependent patients had a larger spike than those managing with oral medications alone.

For patients with both knee osteoarthritis and type 2 diabetes, research on extended-release triamcinolone showed that it delayed the time to peak glucose levels compared with the standard formulation, because the drug enters the bloodstream more slowly.¹⁰ If you have diabetes, let your provider know before the injection so you can monitor glucose closely for the first week and adjust your medication if needed.

Other common side effects include a temporary flush or warmth in the face, mild water retention, and occasionally mood changes for a few days. These are all caused by the portion of steroid that reaches the general circulation and typically pass within a week.

Can Repeated Injections Damage the Cartilage?

This question hangs over every cortisone conversation, and the evidence is mixed enough that it deserves a straight look. Emerging research suggests a possible small risk that repeated intra-articular corticosteroid injections could worsen joint deterioration over the long term.¹¹ The concern is not purely theoretical. Lab studies have shown that certain steroid and local anesthetic combinations increase chondrocyte death in cartilage tissue samples.¹²

The picture gets more nuanced when you look at individual drugs. In vitro work comparing different steroids found that triamcinolone was less toxic to cartilage cells than betamethasone or methylprednisolone, and adding certain local anesthetics worsened the damage.¹³ Another lab study found that combining lidocaine or bupivacaine with betamethasone significantly increased cartilage cell death compared with the anesthetics alone, while triamcinolone showed less toxicity in certain combinations.¹⁴ These are all laboratory findings on isolated cells and tissue samples, not proof that a few knee injections will ruin your cartilage. But they are part of the reason most providers limit cortisone shots to three or four per joint per year and avoid giving them indefinitely.

For most patients getting an occasional injection to manage a flare-up, the short-term pain relief outweighs the theoretical cartilage risk. The concern becomes more relevant for people who have been receiving injections repeatedly over many years, where cumulative exposure could matter.

How Cortisone Stacks Up Against Alternatives

If you are getting a cortisone shot, you may be wondering whether something else would work better or last longer. Two of the most commonly discussed alternatives are hyaluronic acid (viscosupplementation) and platelet-rich plasma (PRP).

A head-to-head trial comparing hyaluronic acid to cortisone for knee osteoarthritis found that both produced statistically significant pain reduction and that the outcomes were similar across multiple measures.¹⁵ Hyaluronic acid does not tend to kick in as fast as cortisone, but some evidence suggests the benefit may last somewhat longer. Still, the comparison is close enough that the choice often comes down to insurance coverage and provider preference.

The PRP comparison is more interesting. In a prospective randomized trial, both PRP and cortisone produced significant pain relief within the first week, with no meaningful difference between them at the five-week mark. But the paths diverged after that: the cortisone group started losing ground around 15 weeks, with pain scores gradually climbing back toward baseline. The PRP group maintained improvement for about 30 weeks before a smaller decline set in at one year.¹⁶ A separate study found the same general pattern: cortisone relief peaked around two months, while PRP benefits were still present at six months.¹⁷ A systematic review confirmed this trend, finding cortisone more effective at the two-month mark but PRP showing sustained benefit through six months.¹⁸

The trade-off is practical: cortisone is cheap, widely covered by insurance, and delivers rapid relief. PRP is expensive, rarely covered, and typically requires multiple sessions. For someone who needs to get through the next few weeks with less pain, cortisone is the faster solution. For someone trying to stretch out relief over several months and willing to pay out of pocket, PRP may offer a longer runway.

The Placebo Component Is Real

Something worth knowing about knee injections in general: a meaningful portion of the benefit comes from the procedure itself, not just the drug. In a clinical trial designed to test a new knee osteoarthritis drug, both the saline placebo group and the sham injection group (where a needle was placed but nothing was injected) showed clinically meaningful improvements in pain and function at every follow-up from four to 24 weeks.¹⁹ That does not mean cortisone is a placebo. The steroid provides genuine anti-inflammatory effects beyond what a sham injection achieves. But it does mean that some of the relief you feel after a knee injection comes from the expectation of relief, the attention of a provider, and possibly the act of aspirating fluid from a swollen joint. Understanding this helps set realistic expectations: if your shot “worked amazingly” last time, part of that experience may not be reproducible with the same drug alone if circumstances or expectations change.

When to Expect a Follow-Up Injection

Most providers space cortisone injections at least three months apart for a given joint. This is partly to limit cumulative steroid exposure to the cartilage and partly because the effect typically wanes within that window anyway. If a shot gives you solid relief for six to eight weeks and then the pain returns, that is considered a normal and successful response. If it barely helps at all or the relief lasts only a few days, your provider may reconsider whether cortisone is the right approach for your knee.

Some patients fall into a pattern of getting injections every three to four months for years. The research on long-term cartilage effects makes this worth questioning if the benefit is modest each time. On the other hand, for someone managing pain while waiting for a knee replacement, regular injections can be a reasonable bridge strategy. The decision is really about weighing tangible short-term pain relief against uncertain long-term joint health, a trade-off that looks different at age 50 than at age 75.

If you have been getting cortisone shots regularly and the relief window keeps shrinking, it is often a sign the arthritis has progressed beyond what corticosteroids can meaningfully address. At that point, the conversation usually shifts toward surgical options, physical therapy intensification, or trialing one of the alternatives like PRP to see whether a different mechanism offers a better match for where your knee is now.