What to Expect After a Cortisone Shot in the Knee?

A cortisone shot in the knee typically brings noticeable pain relief within a few days, with the effect peaking around one to two weeks and lasting anywhere from several weeks to a few months. The procedure itself is quick, but the aftermath involves a short adjustment period that catches many people off guard, from a temporary spike in knee pain right after the injection to possible effects on blood sugar. Understanding what is normal and what warrants a call to your doctor makes the whole experience less stressful.

The First 24 to 48 Hours

Right after the injection, the knee area may feel numb if a local anesthetic was mixed with the steroid. That numbness wears off within a few hours, and when it does, the knee can actually hurt more than it did before the shot. This is completely normal. The steroid has not had time to reduce inflammation yet, and the mechanical act of pushing fluid into a joint creates temporary pressure and irritation.

About one in five people experience what doctors call a “post-injection flare,” a distinct worsening of pain that usually starts within 24 hours. A prospective study of 140 patients found that roughly 21% reported a flare, and younger patients were more likely to develop one. Gender, body mass index, and the specific type of corticosteroid used did not seem to affect flare risk.¹ The flare is self-limiting, meaning it resolves on its own, usually within a day or two. Icing the knee and taking over-the-counter pain medication can help you ride it out.

The distinction between a normal post-injection flare and a sign of something going wrong comes down to timing and additional symptoms. A flare is temporary soreness and swelling that improves steadily after 48 hours. If the pain gets progressively worse after the second day, or if you develop fever, significant redness, or warmth that spreads, those are reasons to contact your doctor promptly, because they could indicate infection.

How Long Until the Shot Actually Works

Cortisone does not work instantly. The steroid needs time to suppress the inflammatory chemicals inside the joint. Most people notice improvement starting around days two to five, with peak relief arriving somewhere between one and two weeks. For some, there is a frustrating limbo period where the local anesthetic has worn off and the steroid has not yet kicked in, which can feel like the shot did not work at all.

The duration of relief varies widely from person to person and depends on how much inflammation was present, the specific steroid formulation used, and the severity of the underlying condition. In knee osteoarthritis, the pain-reducing effect of standard corticosteroid injections tends to be strongest in the first few weeks and then gradually fades. Many providers describe a typical window of roughly four to twelve weeks of meaningful benefit, though some people get relief for longer and others notice pain creeping back sooner.

Rest, Ice, and Getting Back to Activity

You do not need prolonged bed rest after a knee injection, but taking it easy for a short period helps. Research on athletes found that one to two days of rest before ramping back up to activity is a reasonable approach, with potential benefits including maximizing the injection’s effect and reducing systemic absorption of the steroid.² For most non-athletes, that means avoiding long runs, heavy lifting, or intense workouts for a couple of days, not that you need to stay off your feet entirely.

Icing the knee for 15 to 20 minutes at a time during the first day can help with both swelling and any flare pain. After the initial rest period, gentle movement like walking is encouraged. In fact, staying completely immobile can make knee stiffness worse. The idea is to let the steroid settle into the joint without stressing it, then gradually return to your normal routine as the medication starts working.

Blood Sugar Spikes and Other Body-Wide Effects

Cortisone injected into a joint is not supposed to have major effects elsewhere in the body, but some of the steroid inevitably enters the bloodstream. For most people, this produces no noticeable symptoms. For people with diabetes, it is a different story.

A study of diabetic patients receiving corticosteroid injections into the knee found that blood glucose levels increased for two to four days after the injection, with insulin-dependent patients appearing particularly affected.³ If you have diabetes, plan ahead: talk to your endocrinologist or primary care provider about adjusting your insulin or medication in the days after the shot, and monitor your blood sugar more frequently than usual.

Other systemic side effects are uncommon with a single injection but can occur. These include facial flushing, a temporary rise in blood pressure, and, with repeated injections over time, effects on bone density and the adrenal glands’ ability to produce cortisol naturally.⁴ Facial flushing is probably the most commonly reported one. It shows up as a warm, reddish flush on the face and sometimes the chest, typically lasting a day or two. It is harmless but can be alarming if you were not warned about it.

How Serious Is the Infection Risk

Septic arthritis, a joint infection, is the complication that understandably worries people the most. The good news is that it is rare. A large retrospective study looking at over 1.4 million large-joint corticosteroid injections found an absolute risk of about 18 cases per 10,000 patients developing septic arthritis within 21 days.⁵ A separate analysis of over 15,000 intra-articular corticosteroid injections found 14 cases of septic arthritis within six months, with the median time to diagnosis being about three and a half weeks. Patients with inflammatory arthritis or weakened immune systems were disproportionately represented among those who developed infections.⁶

People who have received multiple injections over time may also carry higher risk. A 17-year retrospective review at one hospital found that septic arthritis following joint injections occurred most often after corticosteroid shots, predominantly in the knee, and that nearly half of the affected patients had a history of multiple injections.⁷ The bacterium most commonly responsible was Staphylococcus aureus, a common skin organism. This is why sterile technique during the injection matters. Warning signs of a joint infection include worsening pain after the first couple of days, significant swelling, redness, warmth, and fever. If you notice these symptoms, seek medical attention quickly, because septic arthritis requires urgent treatment.

What Repeated Injections Do to Your Cartilage

This is the area where the evidence has shifted in ways that surprise people. For years, the conventional thinking was that cortisone injections had no meaningful effect on knee cartilage. More recent data complicates that picture.

A randomized trial published in JAMA compared patients with knee osteoarthritis who received triamcinolone injections every three months for two years against those who received saline injections on the same schedule. The triamcinolone group lost more cartilage over the two-year period, and there was no significant difference in pain between the two groups by the end.⁸ That finding was striking: repeated steroid injections on a fixed schedule appeared to accelerate cartilage loss without providing better long-term pain control than a placebo injection.⁹

However, this does not mean a single cortisone shot will destroy your knee. A systematic review of the broader literature on corticosteroids and cartilage noted that the clinical picture depends heavily on dose and frequency. One earlier trial even found that triamcinolone administered every three months for two years prevented narrowing of joint space as measured by X-ray.¹⁰ The conflicting findings likely reflect differences in imaging methods, patient populations, and how “cartilage damage” is measured.

The practical takeaway is that occasional cortisone injections used strategically to manage flare-ups are unlikely to cause meaningful cartilage harm. Repeated injections on a fixed schedule over years are where the risk accumulates. Particulate corticosteroids, which include the most commonly used formulations like triamcinolone acetonide and methylprednisolone acetate, carry higher risks of cartilage toxicity, calcifications, and tissue atrophy when used repeatedly or at high doses.¹¹ Most orthopedic providers limit cortisone injections to three or four per joint per year, partly for this reason.

Extended-Release Formulations

One of the limitations of standard cortisone shots is that the steroid is released relatively quickly, which is why relief tends to fade after a few weeks. Newer formulations aim to change that. An extended-release version of triamcinolone acetonide packages the drug inside tiny biodegradable microspheres that dissolve slowly within the joint. In a phase III trial, this formulation improved pain, stiffness, and physical function better than both placebo and standard triamcinolone suspension over 24 weeks.¹²

A real-world study looked at patients who had already tried standard cortisone and found the extended-release version provided about seven additional weeks of relief on average. Patients with less severe osteoarthritis tended to benefit the most from the switch.¹³ Another extended-release formulation using a different corticosteroid, fluticasone propionate, showed the potential to provide pain relief for up to 14 weeks in a phase 2 trial, longer than what is typically reported for existing products.¹⁴ These formulations may be worth asking about, especially if standard cortisone shots wear off too quickly for you.

How Cortisone Compares to Hyaluronic Acid and PRP

Cortisone is not the only injection option for knee osteoarthritis, and patients often wonder how it stacks up against alternatives. The two most common comparisons are with hyaluronic acid (a gel-like lubricant injected into the joint) and platelet-rich plasma (PRP, made from a concentrated sample of your own blood).

Cortisone tends to win the short-term pain relief contest. Studies consistently show that corticosteroid injections provide faster and stronger initial pain control than hyaluronic acid. But the picture flips at later time points: hyaluronic acid may offer modest benefits beyond 26 weeks, a time frame when cortisone’s effect has generally faded.¹⁵ Hyaluronic acid is sometimes described as having a slower onset but a longer tail of effect, which can make it a better fit for people looking for sustained relief rather than quick rescue from a pain flare.¹⁶

PRP has generated a lot of enthusiasm. A randomized controlled trial comparing single injections of PRP versus cortisone in moderate knee osteoarthritis found that both reduced pain after the first week, but at one year the PRP group had a significantly larger reduction in pain scores.¹⁷ A systematic review of randomized trials found that both PRP and cortisone injections are safe and effective, with some evidence suggesting PRP offers more prolonged benefits, though the research community has not reached consensus on whether PRP is clearly superior overall.¹⁸

The trade-offs are practical as well as clinical. Cortisone is inexpensive and almost universally covered by insurance. PRP is often paid out of pocket and can cost several hundred dollars per injection. Hyaluronic acid falls somewhere in between on cost and insurance coverage varies. If you need fast relief from a painful flare, cortisone is hard to beat. If you are managing chronic knee arthritis and want something with potentially longer-lasting effects, the alternatives are worth discussing with your provider.

If You Are Considering Knee Replacement Surgery

Timing a cortisone shot relative to a planned knee replacement is something your surgeon should know about. Research shows that a corticosteroid injection given within two weeks before total knee arthroplasty roughly triples the risk of postoperative infection.¹⁹ A meta-analysis confirmed that injections within three months of surgery increased the risk of periprosthetic joint infection.²⁰ The steroid appears to suppress the local immune environment in the joint, making it harder for the body to fight off bacteria introduced during surgery.

The strongest evidence points to the highest risk being in the first two to four weeks after the injection, with the risk tapering off over the following months. Most surgeons prefer to wait at least three months between a cortisone shot and a scheduled knee replacement. If you are on a waitlist for surgery or your doctor has been discussing joint replacement as a next step, let them know before you get another injection so you can plan the timing accordingly.

Does It Matter How the Injection Is Given

You might assume that getting a needle into a knee joint is straightforward given its size, but accuracy is not guaranteed when the injection is done by feel alone. A review of the evidence found that ultrasound-guided knee injections had a 96% accuracy rate for landing inside the joint space, compared to about 78% accuracy with the traditional landmark-based approach.²¹ When the steroid ends up outside the joint, it does not work as well and can cause problems like fat atrophy or skin discoloration at the injection site.

In practice, many orthopedic surgeons and sports medicine doctors inject knees without ultrasound and get good results, particularly when there is a noticeable joint effusion (fluid buildup) that makes the knee easier to access. Where ultrasound guidance tends to matter most is in patients who are obese, have minimal effusion, or have unusual anatomy. If you have had a previous injection that seemed to do nothing, it is reasonable to ask whether ultrasound guidance might be used for the next one. Not every clinic has the equipment readily available, but the technology is increasingly common, especially in radiology and sports medicine offices.

Rare but Serious Complications

Beyond infection, other serious complications from knee cortisone injections are uncommon but worth knowing about. Osteonecrosis, where bone tissue dies due to disrupted blood supply, has been reported in association with repeated steroid injections. Case reports describe young patients developing large osteonecrosis lesions in the knee that required surgical repair with osteochondral grafting.²² These cases tend to involve higher cumulative steroid exposure rather than a single injection. Tendon weakening, skin depigmentation around the injection site, and local fat or muscle atrophy are also documented but infrequent effects, especially with isolated injections.¹¹

The pattern across all of these rarer complications is consistent: the risk scales with the number and dose of injections. A single, well-placed cortisone shot for a painful knee is among the lower-risk procedures in orthopedic medicine. The calculus changes when injections become a regular habit over years, which is part of why physicians limit how often they will offer them. If your knee pain keeps returning after each injection wears off, that recurring pattern is itself useful information. It usually means the underlying problem has progressed to the point where other treatments, including physical therapy, bracing, weight management, or surgical options, deserve a serious conversation.