The three most common injections for knee pain are corticosteroid (cortisone) shots, hyaluronic acid (gel) shots, and platelet-rich plasma (PRP) injections. Each works differently, lasts a different amount of time, and suits different stages of knee problems. Most people receiving these injections have osteoarthritis, though some are used for ligament and tendon injuries as well.
Corticosteroid (Cortisone) Injections
Cortisone shots are the most widely used knee injection and typically the first one offered. They contain a powerful anti-inflammatory medication that’s injected directly into the joint, where it reduces swelling and pain. Most people notice improvement within a few days, and the effects generally last several weeks to a few months.
Because the relief is temporary, cortisone shots are usually limited to a few per year in the same joint. Repeated injections over time can weaken cartilage and surrounding tissue, so doctors use them strategically rather than on a fixed schedule. They work best for flare-ups of osteoarthritis or when you need short-term relief to participate in physical therapy or get through a particularly painful stretch.
The most common side effect is a “postinjection flare,” a temporary spike in pain and swelling that can affect roughly a third of patients within the first day or two. It resolves on its own. Serious complications like joint infection are extremely rare, occurring in fewer than 1 in 100,000 injections.
Hyaluronic Acid (Gel) Injections
Sometimes called gel shots, viscosupplementation, or even “rooster comb” injections, these add hyaluronic acid to your knee joint. Hyaluronic acid is a naturally occurring substance in joint fluid that acts as a lubricant and shock absorber. In osteoarthritis, levels of this substance drop, which contributes to stiffness and pain. Gel shots aim to restore some of that cushioning.
Unlike a single cortisone shot, hyaluronic acid often requires a series of injections, typically one shot per week for three or four consecutive weeks. Some newer formulations are designed as a single injection. Relief tends to build gradually and can last several months, potentially longer than a cortisone shot for some people.
A head-to-head study comparing the two found that both corticosteroid and hyaluronic acid injections produced similar modest improvements in pain and function at three and six months. Neither was clearly superior, which means the choice often comes down to your specific situation, how your body responds, and whether you’ve already tried one type without success.
Medicare covers hyaluronic acid injections when you have symptomatic knee osteoarthritis that interferes with daily activities like walking or standing, and when simpler treatments like physical therapy and over-the-counter pain relievers haven’t provided adequate relief. Private insurance policies vary, so checking your plan before scheduling is worthwhile.
Platelet-Rich Plasma (PRP) Injections
PRP injections use your own blood. A sample is drawn, spun in a centrifuge to concentrate the platelets (the part of blood rich in growth factors), and then injected into the knee. The idea is that these concentrated growth factors stimulate healing and reduce inflammation at the cellular level.
Research supports PRP for mild to moderate knee osteoarthritis, and it’s also used for soft tissue injuries involving tendons and ligaments around the knee. Some patients report longer-lasting relief compared to cortisone, though results vary widely from person to person. PRP typically requires one to three injections spaced a few weeks apart.
The biggest practical difference with PRP is cost. Most insurance plans, including Medicare, do not cover it, so you’ll likely pay out of pocket. Prices vary by clinic and region but commonly run several hundred dollars per injection. Because the injection uses your own blood, allergic reactions are essentially nonexistent, making it the option with the fewest side effects.
How to Choose Between Them
Your doctor’s recommendation will depend on the severity of your knee damage, what you’ve already tried, and how quickly you need relief. Cortisone is often the starting point because it’s fast-acting, widely available, and covered by insurance. If cortisone stops providing meaningful relief or you want a longer-lasting option, hyaluronic acid or PRP are the typical next steps.
None of these injections cure osteoarthritis or reverse cartilage loss. They manage symptoms, and they work best when combined with other strategies like strengthening exercises, weight management, and activity modifications. Think of them as tools that buy time and improve quality of life, not permanent fixes.
What to Expect During and After the Injection
All three injections follow a similar process. You’ll sit or lie down, the skin around your knee is cleaned, and the injection is administered with a standard needle. Some doctors use ultrasound guidance to place the needle precisely inside the joint. The procedure itself takes only a few minutes.
Afterward, you can resume normal activities but should avoid strenuous exercise or anything that puts heavy strain on the knee for about 48 hours. Avoid soaking the injection site (baths, pools, hot tubs) for 24 hours. Showers the next day are fine. Some soreness or mild swelling at the injection site is normal and usually fades within a day or two. Icing the knee for 15 to 20 minutes at a time can help with any post-injection discomfort.