Cortisone shots are a common medical treatment used to manage pain and inflammation in specific areas of the body. The injection delivers a potent anti-inflammatory medication, a synthetic version of the hormone cortisol, directly into or around a joint, tendon sheath, or bursa. This localized delivery offers powerful relief by calming the immune response at the site of injury or disease, such as arthritis or tendinitis. While these injections can provide significant therapeutic benefit, it is important to understand the associated risks and potential side effects before undergoing the procedure.
Immediate and Temporary Side Effects
The most frequently encountered reactions occur shortly after the injection and are typically mild and short-lived. One common experience is the post-injection “steroid flare,” which is a temporary increase in pain and inflammation at the injection site. This flare is a reaction to the injected corticosteroid crystals, typically peaks within the first 24 hours, and resolves spontaneously within one to three days.
Many patients also experience temporary systemic effects, such as facial flushing or hot flashes. This effect is a transient reaction to the medication entering the bloodstream, usually appearing within the first day and subsiding after 48 hours. Localized side effects at the injection site are common, including minor bruising or temporary bleeding just under the skin. Some individuals may also notice a temporary, mild elevation in blood pressure a few hours following the injection.
Localized Tissue Complications
Corticosteroids are powerful agents, and when concentrated at the injection site, they can cause changes in the surrounding soft tissues. Subcutaneous fat atrophy, or lipoatrophy, is a recognized complication where the fat cells near the skin’s surface are dissolved, resulting in a visible indentation or dimpling. This effect is often caused by concentrated steroid crystals outside the intended target area.
Skin depigmentation, or hypopigmentation, is another localized cosmetic change, appearing as a lighter patch of skin at the site of the injection. This is thought to be due to the medication altering the function of melanocytes. While both fat atrophy and depigmentation are usually temporary, they can take a significant amount of time to resolve, with spontaneous improvement often requiring six to thirty months.
A more concerning local risk involves the structural integrity of tendons and cartilage, particularly with repeated or high-dose injections. Corticosteroids suppress collagen synthesis, which may weaken the tissue and increase the risk of tendon rupture. Therefore, clinicians generally avoid injecting the medication directly into a tendon, as this poses the highest risk of damage. Similarly, frequent injections into a joint space, especially weight-bearing joints, have been shown to accelerate the degradation of joint cartilage over time due to the drug’s toxic effect on the cells.
Systemic Physiological Effects
Even though the injection is local, some of the corticosteroid medication is absorbed into the bloodstream, leading to temporary systemic effects. A common metabolic effect is a transient but notable spike in blood glucose levels, which can last for several days to a week after the procedure. This is a particular concern for individuals with diabetes, who must closely monitor their sugar levels and may need to temporarily adjust their medication dosage in consultation with their healthcare provider.
The medication can also temporarily affect the endocrine system, leading to suppression of the hypothalamic-pituitary-adrenal (HPA) axis, resulting in secondary adrenal insufficiency. This condition occurs because the body’s natural cortisol production is temporarily halted, and while it is often asymptomatic, it can last for two to four weeks. Corticosteroids also cause a temporary reduction in immune cell numbers and cytokine function. This mild immune suppression can last for one to four weeks, meaning the body’s defenses may be slightly lowered during that period.
Factors That Increase Risk
The overall safety of a cortisone shot is influenced by patient factors and procedural guidelines. To mitigate the risk of localized tissue damage, such as cartilage degradation and tendon weakening, most healthcare providers limit the number of injections into a single joint or area to three or four per year. Exceeding this frequency increases the likelihood of long-term structural harm.
Pre-existing health conditions also influence risk, particularly severe or poorly controlled diabetes, which can be destabilized by the temporary blood sugar spike. A current infection at the site of injection or elsewhere in the body is another major contraindication. Corticosteroids can activate a quiescent infection or the injection itself can introduce bacteria into the joint space, leading to a severe complication called septic arthritis. Although rare, septic arthritis can be catastrophic and is often linked to breaches in sterile technique.
Taking blood-thinning medications, or anticoagulants, increases the risk of bleeding at the injection site. While the risk of major bleeding complications in peripheral joint injections is low, patients on these medications may need to temporarily stop them or take specific precautions before the procedure, especially if the injection is near the spine where a hematoma could cause serious neurological damage.