A cortisone shot in the shoulder is a common medical procedure that involves injecting a corticosteroid medication, often combined with a local anesthetic, directly into or around the joint space. This treatment is primarily used to address intense localized pain and inflammation stemming from conditions like rotator cuff tendinitis, impingement syndrome, or bursitis. Cortisone, a powerful anti-inflammatory drug, works by mimicking the effects of cortisol, a hormone naturally produced by the adrenal glands. The injection’s purpose is to reduce swelling and irritation, providing a window of pain relief that allows the patient to participate fully in physical therapy and rehabilitation.
Expected Post-Injection Reactions
The most immediate and common side effect patients encounter is a temporary increase in discomfort known as a “cortisone flare.” This reaction typically involves a short-lived worsening of pain, swelling, and sometimes local warmth at the injection site, usually starting within the first 24 to 48 hours. The flare is caused by the body’s reaction to the corticosteroid crystals that are deposited in the tissue, triggering a localized inflammatory response. Though unsettling, this reaction is generally mild and self-limiting.
To manage the initial soreness and the potential flare, medical professionals often advise protecting the shoulder and applying ice to the area for short periods. The local anesthetic mixed with the cortisone provides immediate, but short-lived, numbness. Pain may return or intensify once this numbing agent wears off. Patients should understand that this temporary pain does not indicate the injection has failed, as the anti-inflammatory effects of the corticosteroid typically begin to take effect within three to seven days.
Localized Skin and Tissue Changes
Certain side effects are confined to the physical injection site and the surrounding soft tissues, occurring due to the localized action of the steroid. One such effect is subcutaneous fat atrophy, which is the localized loss of the fatty tissue layer beneath the skin. This can result in a visible depression or dimple in the skin surface at the site where the injection was administered.
Another aesthetic change is skin depigmentation, also called hypopigmentation, where the skin around the injection site becomes lighter in color. This effect is more noticeable in individuals with darker complexions. While these localized effects are not medically serious, they can be long-lasting; atrophy and depigmentation may take six to thirty months to resolve spontaneously and can occasionally be permanent. The risk of these dermal changes is reduced when the injection is delivered deeply into the joint or bursa, rather than superficially into the fat or skin layer.
Systemic Side Effects
When the corticosteroid is absorbed from the injection site into the bloodstream, it can cause transient effects throughout the body. A primary systemic concern is the temporary increase in blood glucose levels, which is particularly relevant for individuals with diabetes. The corticosteroid can impair the body’s ability to process sugar, leading to a spike in blood sugar that may peak between 2 and 84 hours after the injection.
This transient hyperglycemia usually resolves within a few days, but patients with diabetes should monitor their glucose levels more frequently for up to a week following the procedure. Other systemic reactions include a temporary steroid flush, characterized by a feeling of warmth and redness in the face and chest. Additionally, some individuals may experience minor psychological changes, such as temporary insomnia, anxiety, or irritability. Though a single shot rarely causes significant long-term issues, the medication can transiently suppress the hypothalamic-pituitary-adrenal (HPA) axis, which is the body’s natural stress response system.
Rare and Severe Complications
While a cortisone shoulder injection is generally safe, there are infrequent but serious complications that warrant immediate medical attention. Joint infection, medically termed septic arthritis, is a rare but potentially devastating complication that occurs when bacteria are introduced into the joint space during the procedure. Signs of a developing infection include disproportionate and increasing pain, swelling, warmth, and redness that begin several days after the injection, often accompanied by a fever. Septic arthritis is a medical emergency that requires swift diagnosis and treatment to prevent permanent joint damage.
Another serious risk, particularly in the shoulder, involves damage to the surrounding connective tissues. Corticosteroids can weaken tendons by inhibiting the cells responsible for tissue repair and collagen synthesis. This weakening raises the risk of tendon or ligament rupture, especially if the steroid is injected directly into the tendon fibers of the rotator cuff. Some studies have indicated an increased incidence of full-thickness rotator cuff tears in patients who received subacromial corticosteroid injections. Finally, immediate signs of an allergic reaction, such as hives, difficulty breathing, or swelling of the throat, are extremely rare but require emergency medical response.