Cortisone shots, or corticosteroid injections, are a medical tool used to reduce inflammation and relieve pain in a targeted area, such as a joint, tendon, or bursa. This powerful anti-inflammatory effect offers significant relief for conditions like arthritis and tendonitis. While these injections are effective for managing symptoms, they deliver a potent dose of medication. Patients should understand that this localized treatment carries potential negatives that range from temporary discomfort to structural changes and systemic effects.
Temporary and Immediate Reactions
The most common negative experience following a cortisone injection is a post-injection flare. This temporary increase in pain and swelling at the injection site occurs in approximately 1 in 5 patients and can feel worse than the original discomfort. The flare is caused by the body’s reaction to the corticosteroid crystals deposited in the tissue, and it typically subsides within 24 to 48 hours.
Some people also experience a temporary steroid flush, characterized by warmth and redness, often across the face and chest. This harmless side effect usually resolves within a few days. Minor changes in mood, such as temporary irritability or sleeplessness, are also reported immediately following the injection. These short-lived effects are self-limiting and do not indicate a serious complication.
Structural Changes at the Injection Site
The potent anti-inflammatory action of the steroid can sometimes have a destructive effect on the surrounding tissues. One noticeable local side effect is subcutaneous fat atrophy, which presents as an indentation or dimpling of the skin at the injection site. This occurs because the corticosteroid causes a localized loss of fat cells beneath the skin, creating a depression that is mainly a cosmetic concern.
The injection can also lead to skin depigmentation, where the skin over the area becomes lighter, a condition known as hypopigmentation. This effect is particularly visible in individuals with darker skin tones. Furthermore, if the steroid is injected directly into a tendon, the medication can weaken the collagen structure, increasing the risk of tendon rupture. Physicians must exercise extreme care to ensure the medication is delivered adjacent to, rather than directly into, the tendon tissue.
Systemic Effects on Major Body Functions
Even though the shot is localized, the corticosteroid is absorbed into the bloodstream and can temporarily affect the body’s overall physiology. For patients with diabetes, a single cortisone injection can cause a significant, temporary elevation in blood glucose levels. This spike typically lasts for several days to a week, requiring diabetic patients to monitor their sugar levels closely and potentially adjust their medication with their doctor’s guidance.
The absorbed steroid can also cause a transient increase in blood pressure, which usually returns to baseline within a week or two. Additionally, the body’s internal hormone regulation system, known as the hypothalamic-pituitary-adrenal (HPA) axis, can experience temporary suppression. This happens because the injected steroid acts like the body’s natural stress hormone, cortisol, signaling the adrenal glands to temporarily reduce their own production.
While a single, localized injection is not typically a concern, this HPA axis suppression is why high-dose or frequent systemic steroid use requires a careful tapering schedule. The temporary suppression of the immune response is also a minor systemic effect, which could slightly increase the risk of infection, though this remains a rare complication.
Limits on Injection Frequency and Cumulative Effects
Due to the medication’s potency, medical professionals place strict limits on how frequently a cortisone shot can be administered to the same area. A common guideline suggests limiting injections to no more than three or four times per joint per year, with a minimum interval of at least three months between treatments. This constraint is primarily intended to protect the delicate articular cartilage within the joint.
Repeated exposure to corticosteroids has been associated with progressive damage and loss of joint cartilage, which can accelerate the underlying joint degeneration the treatment was initially meant to alleviate. Furthermore, the effectiveness of the injection can diminish over time, a concept known as diminishing returns. Respecting the frequency limits helps preserve both the long-term health of the joint and the therapeutic utility of the treatment.