Knee Injections’ Side Effects

Knee Injection

"File:Injection-knee-ama-regenerative-medicine.jpg" by [Alice Pien, MD] is licensed under CC BY-SA 4.0

Therapeutic knee injections deliver medicine directly inside the knee joint and are used to reduce painful symptoms, which are often caused by knee arthritis.

There are a few injection options available to help relieve knee pain, including corticosteroids, hyaluronic acid (viscosupplementation), platelet-rich plasma (PRP), dextrose prolotherapy, and saline prolotherapy. Different injections are used depending on the type of knee pain, the cause, and factors such as age and other medications you might also be taking.

While knee injections are generally safe and the risk of complication low, there are some potential side effects you may experience after an injection. It is important to discuss the different knee injection options with your healthcare provider—including the potential side effects—as you consider the most appropriate treatment plan for you. 

That said, according to the American Academy of Orthopedic Surgery, evidence supporting the effectiveness of cortisone and PRP are inconclusive, with PRP and stem cells being more recent, and thus with less available evidence about their effectiveness. and viscosupplementation showing strong evidence of not being effective.


Corticosteroid injections (cortisone) are often administered for the treatment of knee joint pain and symptoms of osteoarthritis involving the knee.

These injections are used most often to reduce pain and inflammation for people who have: 

Common Use

A corticosteroid injection may quickly reduce inflammation in the body, offering knee pain relief that can last for two to three months, and sometimes longer. The temporary pain relief may provide an opportunity to engage in physical therapy, attend an important life event, or postpone knee replacement surgery.

Before receiving a cortisone injection, the area around the injection site will be cleaned. Your healthcare provider may administer a local anesthetic to numb the area for the injection. In some cases, your healthcare provider may use an ultrasound to observe and direct the needle placement. The medication is released directly into the knee at the injection site.

Side Effects

While cortisone injections can be helpful at providing temporary relief, they are not a cure for knee pain and may not work well for everyone. Cortisone injections may cause side effects, particularly when used repeatedly. 

Most are minor and go away with time. However, if you are experiencing persistent or increasingly intense side effects, speak with your healthcare provider.

Side effects can include:

  • Cortisone flare reaction: Discomfort at the injection site may cause an increase in pain 24-48 hours after the injection. Icing the injection site may help with this temporary flare of pain. 
  • Elevated blood sugar levels: Speak to your healthcare provider if you have diabetes before receiving a cortisone injection, as steroids can cause blood glucose (sugar) levels to rise.
  • Loss of fatty tissue: High doses of cortisone can lead to dimpling of the skin or thinning of fat in the area.
  • Skin pigment changes: A loss of pigmentation may be noted, and can be permanent.

High Levels of Exposure

Cortisone—especially when used on a long-term basis—may break down tissues, such as tendons, ligaments, and cartilage in the knee joint. Cartilage acts as a shock absorber, reducing the friction between bones as they move.

For this reason, it is not recommended to get repeated cortisone injections in the same joint over a short period of time, as it may cause more harm than good. If more than one injection is given in the same joint, the injections should be scheduled at appropriate intervals. Patients should not receive more than three to four cortisone injections per year.

Anytime a needle is injected into the skin, there is a chance of infection. An antiseptic will be applied to the skin prior to injection to reduce the risk of infection.

Hyaluronic Acid

Hyaluronic acid injections have been used to help reduce the joint pain caused by arthritis. Viscosupplementation delivers lubricating fluid directly into the knee joint to provide temporary relief of knee pain and inflammation.

Hyaluronic acid injections help improve knee function, and may even slow the progression of the disease. 

Brand names of hyaluronic acid injections include:

Before administering the injection, your healthcare provider will sterilize the skin around the injection site. Then, a local anesthetic will be applied (topically or injected) to prevent discomfort during the procedure. 

If the knee joint is swollen with excess fluid, your healthcare provider may first withdraw excess fluid to relieve pressure before the injection. 

Your healthcare provider will inject the hyaluronic acid into the affected joint. Many patients are advised to place ice on the injection site afterward to reduce pain and swelling. 

Common side effects of hyaluronic acid injections include: 

  • Headache 
  • Pain at the injection site
  • Rash/itching
  • Swelling of the knee
  • Upset stomach (e.g., nausea, diarrhea) 

Most of these side effects are temporary and go away with time. If your side effects are persistent or progressively worsen, seek medical attention. 

Dextrose Prolotherapy and Saline Prolotherapy

Prolotherapy is the injection of an irritant solution into joints to stimulate natural tissue repair. Prolotherapy injections most often use a sugar solution (dextrose) or salt solution (saline) to temporarily: 

  • Improve strength, function, and mobility of the joint
  • Increase the strength of ligaments, tendons, and other tissues surrounding the joint
  • Reduce pain, stiffness, and inflammation in the joint

Prolotherapy typically involves multiple injections made during one treatment session. These treatments are given monthly over the course of several (three to six) months, followed by as-needed injections. Fewer treatments may be required, depending on the individual and severity of their condition.

Healing time varies from person to person, but many people experience relief of painful symptoms within three to four days after the treatment. Because of the healing process, it may take up to a few weeks to experience full relief.

Prolotherapy injections are generally safe and come with few risks. However, the treatment may cause mild side effects, including:

  • Bruising 
  • Headache
  • Infection at the injection site 
  • Pain, swelling, and stiffness in the area surrounding the injection

Other Injections

  • Platelet-rich plasma therapy (PRP) is used to help relieve symptoms of knee pain. PRP involves extracting blood from the patient’s arm and separating the platelet-rich plasma from the rest of the blood’s components. The PRP is then injected into the joint. The idea is to use the natural healing properties of the blood to repair damaged tissue.
  • Stem cell injections use cells that are typically collected from a patient’s own tissues, blood, or bone marrow. The theory is that—when injected into an arthritic joint—the stem cells may develop into cartilage cells, slowing down degeneration and reducing pain and inflammation.

At present time, there is limited evidence on the efficacy of stem cell injections for knee pain caused by osteoarthritis. Stem cell injections and PRP are not standard practice, and the formula concentrations are not standardized.

Due to the lack of studies proving safety and efficacy, the American College of Rheumatology and the Arthritis Foundation advise against platelet-rich plasma or stem cell injections.

A Word From Verywell

Before deciding to proceed with having knee injections, you may like to try alternatives to relieve the pain and inflammation in your knee.

These options include:

  • Lifestyle modification: This may include weight loss and modifying your exercise regimen to incorporate low-impact activities.
  • Exercise and physical therapy: Many forms of knee pain can be managed with proper exercise. Exercise, whether or alone or with a physical therapist, will focus on stretches and strengthening muscles around the joints to help relieve pain and increase mobility.
  • Bracing: Knee braces can be used to provide external stability to the joint. Devices that put pressure on the sides of the joint may help the joint to realign, with the intent to decrease pain and inflammation. There are many brace options, so speak to your healthcare provider about which may work best for you. 
  • Anti-inflammatory medications: Over-the-counter and prescription medications can be used to temporarily reduce inflammation and pain in the knee. Non-steroidal anti-inflammatory medications (NSAIDs) are most often prescribed or recommended to reduce inflammation in the body to provide temporary relief of arthritis symptoms, including joint pain.

If you opt for knee injections, it is important to discuss your health history (including allergies) and current medications you are taking with your healthcare provider. This includes over-the-counter medications, herbal remedies, vitamins, and prescription medications.

9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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