Why Are Cortisone Shots Bad for Your Body?

Cortisone shots deliver a powerful anti-inflammatory steroid directly into a painful joint, tendon, or soft-tissue site, and they genuinely work for short-term relief. The trouble is that the same drug that quiets inflammation can also damage the tissue it is meant to protect. Cartilage cells die faster, tendons weaken, blood sugar spikes in people with diabetes, and the body’s own stress-hormone system can get thrown off. None of this means cortisone injections are useless, but the potential harms are more varied and better documented than many patients realize.

Cartilage Takes a Hit

The concern researchers keep coming back to is what cortisone does to cartilage cells. A large scoping review of lab and animal studies found that well over half of the studies examined showed evidence of chondrotoxic effects from corticosteroids, meaning the drug was directly toxic to the cells that keep your joint surfaces smooth and resilient.¹ That toxicity gets worse when cortisone is mixed with a local anesthetic, which is common practice. One study showed that combining a glucocorticoid with a local anesthetic increased chondrocyte death beyond what either drug produced alone, with a clear time-dependent drop in cell viability the longer the exposure lasted.²

These are lab findings, so they do not automatically translate one-to-one into your knee. But imaging studies point in the same direction. A systematic review and meta-analysis of MRI and X-ray data found that people who received corticosteroid injections for knee osteoarthritis were roughly twice as likely to show worsening cartilage structure compared with those who did not get injections.³ A separate study using data from the Osteoarthritis Initiative, a large observational cohort, confirmed that corticosteroid injections were associated with greater structural progression of osteoarthritis on MRI than either hyaluronic acid injections or no injection at all over a two-year follow-up.⁴

The practical worry here is straightforward: if you are getting cortisone shots to manage an arthritic knee, you may be trading a few weeks of less pain for faster wear on the joint you are trying to preserve.

Tendons Weaken, at Least Temporarily

Cartilage is not the only tissue that suffers. A systematic review of basic science studies on rotator cuff tendons found that cortisone injections decreased cellular proliferation, reduced tendon stiffness, and lowered the maximum load a tendon could bear before failing. Biomechanical testing in rat shoulders showed these effects persisted for about two weeks after the injection, though they appeared to resolve by three to four weeks.⁵ Histological analysis confirmed the mechanism: fat cells infiltrated the tendon and collagen fibers thinned out, changes that seemed transient but could matter if you stress the tendon during that vulnerable window.⁶

The clinical lesson is that a cortisone shot into or near a tendon is not a green light to immediately load that tendon hard. The tissue needs time to recover its structural integrity. For tendons already under strain, the temporary weakening may be enough to tip things toward a tear.

The Plantar Fascia Problem

One place where the tendon-weakening risk plays out dramatically is the bottom of the foot. Cortisone injections for plantar fasciitis are common, but a systematic review of plantar fascia ruptures found that the vast majority of patients with ruptures had received corticosteroid injections beforehand.⁷ An earlier study that tracked outcomes at a single large practice reported that out of 51 patients diagnosed with plantar fascia rupture, 44 of those ruptures followed a cortisone injection. The authors noted that these ruptures could cause long-term complications that were difficult to resolve.⁸

This does not mean every cortisone shot for heel pain ends badly. Plenty of patients get relief without incident. But the plantar fascia is a structure under constant mechanical load from walking and standing, and the temporary weakening that cortisone causes can be enough to cause it to give way entirely in some people.

Blood Sugar Spikes for People With Diabetes

Cortisone does not stay neatly in the joint. It gets absorbed into the bloodstream, and one of the clearest systemic effects is a rise in blood glucose. A study that tracked fasting blood sugar in diabetic patients after hand and wrist injections found a significant spike on the first day after the shot (an average increase of about 43 mg/dL), a smaller but still meaningful rise on day two, and a return to baseline by day four.⁹ People with type 1 diabetes and those using insulin saw the largest jumps.

The pattern holds for shoulder injections too. One study of people with type 2 diabetes found that the average glucose level rose from about 136 mg/dL before the injection to 159 mg/dL over the first three days. Four out of 25 patients experienced new glucose readings above 350 mg/dL, a level that can be dangerously high.¹⁰ Interestingly, research has also suggested that the injection site matters: knee injections produced a more significant fasting glucose rise than hand or wrist injections, likely because the knee joint is larger and absorbs more steroid into the bloodstream.¹¹

If you have diabetes and are considering a cortisone injection, the practical step is to monitor your blood sugar more closely for about three days afterward and have a plan with your doctor for managing temporary highs.

Your Stress-Hormone System Can Be Suppressed

Your adrenal glands produce cortisol, the body’s natural version of cortisone, as part of the stress response. When you inject a synthetic corticosteroid, your brain registers the flood of steroid and dials down its own production. This suppression of the hypothalamic-pituitary-adrenal axis can happen even after a single injection, and the degree depends on the size of the joint injected, the drug used, the dose, and how many injections you have received.¹²

For most people getting an occasional knee or shoulder injection, this suppression is mild and temporary. The concern becomes serious for patients who receive repeated injections, multiple injections in different joints around the same time, or injections with long-acting preparations like triamcinolone acetonide. In extreme cases, enough systemic absorption can trigger iatrogenic Cushing syndrome (the body acting as though it is chronically overdosed on cortisol) or, on the flip side, leave the adrenal glands too suppressed to mount a normal cortisol response during surgery, illness, or trauma.¹³ That failure to respond appropriately to stress is called adrenal crisis, and it is a medical emergency.

Immune Suppression and Vaccine Timing

Because the steroid is absorbed systemically, it temporarily dampens your immune system. A narrative review found that immune cells involved in fighting off infections are suppressed for about 48 hours after an injection, while key signaling molecules that coordinate the immune response remain suppressed for over 96 hours.¹⁴ During that window, your body is less equipped to fend off a new infection or mount a strong response to a vaccine.

This has practical implications for vaccination schedules. A multispecialty position statement recommends that if a cortisone injection is non-urgent, it should be scheduled at least one week before or after a planned vaccination to avoid blunting the immune response to the vaccine.¹⁵ For healthy patients on a tight schedule, the injection and vaccine can be given closer together after a discussion about the tradeoff, but the default guidance is to space them out.

Infection Risk Before Joint Replacement Surgery

One of the most serious practical consequences of cortisone injections is the elevated risk of infection when joint replacement surgery follows too closely. In a study of over 76,000 total knee arthroplasty patients, receiving a corticosteroid injection within two weeks of surgery nearly tripled the odds of a postoperative infection.¹⁶ A separate meta-analysis concluded that injections within three months of total knee replacement increased the risk of periprosthetic joint infection, a devastating complication that often requires additional surgery.¹⁷ Another large study found that patients injected with any corticosteroid within 90 days of knee replacement had a periprosthetic infection rate of about 1.6%, roughly four times higher than the 0.4% rate in patients who did not receive a preoperative injection.¹⁸

If you are getting cortisone shots to manage knee pain and a knee replacement is on the horizon, this timing question is one to discuss carefully with your surgeon. The evidence suggests that waiting at least three months between the last injection and surgery meaningfully reduces the infection risk.

Skin Changes and Post-Injection Pain Flares

Two local side effects catch patients off guard. The first is a change in the skin and fat near the injection site. Cortisone can cause subcutaneous fat atrophy, where the tissue under the skin thins out, sometimes creating a visible dent, and hypopigmentation, a lightening of the skin color. These are caused by steroid crystals depositing in the tissue outside the intended target.¹⁹ In a prospective study of extra-articular injections, hypopigmentation appeared four to ten weeks after the shot and fully resolved over several months, while fat atrophy, which occurred in about 7% of patients (all women in that study), showed incomplete recovery in two out of three cases.²⁰

The second surprise is the post-injection pain flare. About one in five patients experiences a temporary spike in pain after the injection, sometimes lasting a day or two before the anti-inflammatory effect kicks in. A prospective study found that younger patients were more prone to these flares, with odds of a flare decreasing by about 5.5% for each year of age.²¹ Body weight, injection site, and the type of corticosteroid used did not significantly affect whether a flare occurred.

Rare but Severe Bone Damage

In rare cases, a cortisone injection into the hip has been linked to rapid and severe destruction of the femoral head, the ball portion of the hip joint. A case report documented two patients who developed osteonecrosis (bone death) of the femoral head after a single intra-articular corticosteroid injection, with significant bone destruction visible on imaging within 11 to 14 weeks. Both patients ultimately required total hip replacement.²²

On the broader question of whether cortisone shots increase fracture risk in general, the evidence is more reassuring. A large study published in JAMA Network Open analyzed cumulative cortisone injection doses and found no association between higher doses and fracture risk, even in patients with osteoporosis.²³ So the bone risk appears to be concentrated in specific joints and rare destructive events rather than a systemic weakening of the skeleton.

Short-Term Gain, Long-Term Pain

Perhaps the most underappreciated problem with cortisone shots is a paradox: the short-term relief can come at the expense of worse outcomes down the road. A randomized controlled trial in patients with tennis elbow (lateral epicondylalgia) compared cortisone injection against physiotherapy and placebo. Cortisone provided superior relief in the first few weeks. But by six months, the injection group was doing significantly worse across measures of pain, disability, and quality of life. At one year, more than half of the patients who received cortisone had experienced a recurrence, a substantially higher proportion than the placebo group. Most patients recovered regardless of treatment, reflecting the natural course of the condition, but those who got cortisone were the least likely to report being completely recovered.²⁴

That study is particularly striking because it suggests cortisone did not just fail to help in the long run; it actively interfered with the body’s healing process. The short-term suppression of inflammation may have masked the signals the tissue needs to remodel and repair.

Epidural Injections Carry Their Own Risks

Cortisone injections into the epidural space of the spine, commonly used for back and leg pain from herniated discs, occupy their own risk category. A comprehensive literature review catalogued a range of complications, from relatively common ones like positional headaches (reported in up to 28% of patients) and spinal fluid leaks (up to 6%) to rare catastrophic events including stroke, paralysis, and death. The review also noted a 2012 outbreak in which contaminated steroid vials caused fungal meningitis, sickening hundreds of patients and killing at least 25.²⁵ Neurologic injuries from epidural steroid injections are rare, but when they happen, they can be devastating and irreversible.²⁶

The contamination incident was a failure of compounding pharmacy oversight rather than an inherent property of the drug, but it highlighted how the supply chain adds a layer of risk beyond the pharmacology itself. The broader lesson is that epidural steroid injections should be treated as a genuinely invasive procedure with informed consent, not a routine office visit.

How Emerging Alternatives Compare

With the downsides of cortisone becoming better documented, interest in platelet-rich plasma (PRP) has grown. For rotator cuff injuries, two recent meta-analyses compared PRP and cortisone injections head to head. Pain relief was similar in the short term, but PRP pulled ahead in function scores over the longer follow-up periods. One analysis found that the functional advantage of PRP over cortisone grew progressively, becoming substantial by six months.²⁷ Another meta-analysis reported significantly better shoulder function scores in PRP-treated patients at long-term follow-up.²⁸

PRP is not a magic bullet. It is less well studied overall, more expensive, rarely covered by insurance, and the preparations vary widely between clinics. But the emerging picture is that for conditions where you need longer-term improvement rather than a quick burst of relief, PRP may avoid some of the tissue-damaging trade-offs that come with cortisone.

How Often Is Too Often

Clinical guidelines from a consortium of major pain and spine societies suggest a minimum interval of two to three weeks between cortisone injections to the same site, with intervals of up to three months being reasonable. The series should stop when pain relief has plateaued or is adequate, rather than continuing on a fixed schedule.²⁹ The familiar “three shots and you’re done” rule is not actually grounded in the guidelines, though many doctors use it as a conservative default.

A survey of patients found wide variation in what people believe about injection limits. About 18% thought three injections in the same area was the maximum safe number, while 37% believed there was no fixed limit and that safety depended on dosage. Nearly a third simply did not know.³⁰ The same survey found that the most common source of information about cortisone was friends and family, not doctors, which partly explains why misconceptions persist. Fewer than half of respondents thought the injections were safe, though most of the rest believed safety depended on context rather than viewing them as categorically dangerous.

When Cortisone Shots Still Make Sense

With all these risks, cortisone shots remain a reasonable option in specific situations. Acute flares of inflammatory arthritis, painful bursitis that limits sleep or daily function, and conditions where buying a few weeks of pain relief allows someone to participate in physical therapy are the classic use cases. The key is treating them as a tool with a shelf life rather than a long-term management strategy. For chronic conditions like knee osteoarthritis or tendon problems where the pain keeps returning, the evidence increasingly favors moving toward rehabilitation, load management, and possibly PRP rather than stacking up cortisone injections.

The risks are real but manageable with good clinical decision-making. The bigger problem is that many patients receive cortisone injections without a clear conversation about what the shot can and cannot do, how long the benefit typically lasts, and what the alternatives are. Nearly two-thirds of patients in the survey mentioned above got their information about cortisone from sources other than their treating physician.³⁰ That gap between what the evidence shows and what patients understand is arguably the most fixable problem in the whole equation.