A cortisone shot in the knee is a common treatment for managing joint pain and inflammation, particularly in conditions like osteoarthritis or tendinitis. This injection is a combination of a potent corticosteroid, the anti-inflammatory medication, and usually a local anesthetic, such as lidocaine or bupivacaine. The corticosteroid works by suppressing the immune response and inhibiting inflammatory molecules directly within the joint space, reducing swelling and pain. The primary purpose of the treatment is to provide temporary but significant relief from discomfort and improve joint mobility, allowing the patient to engage in physical therapy or rehabilitation.
Immediate Sensations and the Cortisone Flare
The immediate experience following the injection is often a rapid reduction in pain due to the local anesthetic included. This numbing effect is temporary and typically lasts for only a few hours after the procedure. As the anesthetic wears off, the knee may return to its pre-injection level of pain, or even feel worse.
This temporary increase in discomfort, warmth, and swelling is known as a “cortisone flare” or “steroid flare-up” and is a recognized side effect. The flare is caused by the body’s reaction to the injected corticosteroid crystals, which can irritate the joint lining before they fully dissolve and begin their anti-inflammatory work. This reaction is self-limiting, commonly peaking within the first 24 to 48 hours and then subsiding within one to three days. Experiencing a flare does not indicate the injection has failed; icing the area is usually recommended to help manage these symptoms.
Timeline for Therapeutic Pain Relief
The true therapeutic effect of the corticosteroid is not instantaneous because the medication requires time to fully exert its anti-inflammatory action. After the initial anesthetic wears off and any potential flare subsides, the sustained pain relief typically begins gradually. Most patients start to notice a definite improvement in joint pain and swelling within three to seven days of the injection.
The peak effectiveness of the shot is commonly reached around one to two weeks after administration, once the corticosteroid has had sufficient time to fully reduce the chronic inflammation within the joint. Studies show that about half of patients achieve relief within three days, and over 90% report improvement within eight days. This delayed timeline is why the immediate numbing agent is included, providing comfort while the anti-inflammatory medication starts working.
Post-Procedure Care and Activity Modifications
Managing the knee properly in the days following the injection is important for maximizing the shot’s effect and preventing complications. It is recommended to rest the affected joint and avoid strenuous activity for at least 24 to 48 hours post-procedure. While routine activities like walking are generally permitted, high-impact movements such as running, jumping, and heavy lifting should be avoided for several days to a week.
Temperature Management
Applying ice to the injection site for 10 to 20 minutes at a time can help reduce local soreness, swelling, and the discomfort associated with a cortisone flare. Conversely, you should not use heat, such as heating pads, hot tubs, or whirlpools, for at least two days, as this can potentially increase inflammation. It is also advisable to avoid submerging the knee in a bath or pool for the first couple of days to protect the injection site.
Monitoring for Infection
Patients must monitor the injection site closely for any signs of infection, which is a rare but serious risk. You should contact your healthcare provider immediately if you develop symptoms like a fever over 100 degrees Fahrenheit, severe redness, significant warmth of the entire knee, or pain that worsens significantly after the initial 48-hour flare period.
Duration of Effect and Injection Frequency Limits
The duration of pain relief from a knee cortisone shot varies considerably among individuals and depends on the severity of the underlying condition. Relief commonly lasts anywhere from six weeks to six months, with many patients experiencing symptom reduction for two to four months. It is important to understand that the injection provides temporary symptom management and does not cure the condition causing the inflammation.
Because of concerns that repeated corticosteroid exposure may potentially damage the joint’s cartilage and weaken nearby tendons, there are limits on injection frequency. Most healthcare providers recommend no more than three to four injections into the same knee joint within a 12-month period. Ideally, injections should be spaced out by a minimum of three months to mitigate the risk of cumulative adverse effects. If the period of relief is short-lived, you should discuss alternative or supplemental treatment options with your physician.