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Your health insurance may cover your second opinion.
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Knee injection: everything you need to know about this medical procedure and the products used
Medically reviewed by
Updated on
August 24, 2026
You have been offered a knee injection, or you are considering this option to relieve persistent joint pain. This procedure, common in rheumatology, orthopedics, and traumatology, often raises questions about how it is performed and its actual effects. This guide will help you understand it better.
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Key takeaways
- A knee injection involves injecting medication directly into the joint to reduce pain and inflammation.
- Several products can be injected, including corticosteroids, hyaluronic acid, or, in some cases, PRP (platelet-rich plasma).
- Corticosteroids act quickly (within a few days) but for a short duration. Hyaluronic acid takes longer to work, but its effects can last longer.
- The injection is part of a more comprehensive treatment plan and does not treat the underlying cause of the pain.
Knee injection: a targeted injection to relieve pain
A knee injection is a medical procedure that involves injecting medication directly into the joint, or in the immediate vicinity, using a fine needle.
The goal is to deliver the product as close as possible to the painful area. The injection thus allows for a more targeted pain-relieving effect than oral medication.
The procedure is performed by a doctor, sometimes under ultrasound or fluoroscopic guidance to precisely visualize the needle's path. It is carried out in a clinic or imaging center and does not require hospitalization.
Inflammatory flare-ups or pain resistant to treatment: when to consider an injection
A knee injection aims to relieve gonalgia (knee pain) associated with inflammatory flare-ups.
It may be considered in various situations:
- knee osteoarthritis (gonarthrosis);
- chronic rheumatism (rheumatoid arthritis, gout, etc.);
- inflammation of the synovial membrane (synovitis) ;
- other joint inflammation (for example, related to a meniscus injury) ;
- inflammation of the structures surrounding the joint (bursitis, tendon issues, etc.
Injections are often recommended:
- when pain persists despite oral treatment (painkillers, anti-inflammatories) and/or physical therapy sessions;
- to temporarily relieve pain while awaiting surgery.
A simple procedure performed in a few minutes
A knee injection generally takes about ten minutes. The steps are as follows:
- Preparation and disinfection. The skin around the knee is carefully disinfected to minimize any risk of infection. In some cases, a local anesthetic is administered.
- Potential aspiration. If fluid has accumulated in the joint, the doctor may drain it before the injection.
- Product injection. The chosen medication (corticosteroid, hyaluronic acid, or other) is injected directly into the joint.
- Imaging guidance : the injection can be performed under fluoroscopic or ultrasound guidance.
After the injection, a brief observation period may be required before returning home. The doctor will also explain what to expect following the procedure and which symptoms would necessitate a follow-up consultation.
Corticosteroid, hyaluronic acid, or PRP injections: different approaches
Different types of products can be injected depending on the situation:
- Corticosteroids (cortisone) have a powerful and rapid anti-inflammatory effect, which is particularly useful during a painful flare-up accompanied by swelling.
- Hyaluronic acid, also known as viscosupplementation, is a natural component of the fluid that lubricates the joint (synovial fluid). Its effect is more gradual.
- Platelet-rich plasma (PRP) is prepared from the patient's own blood. This treatment is not currently officially recommended, although its use is becoming more common in practice.
Only corticosteroid injections are covered by health insurance. Regardless of the product chosen, intra-articular injections act on pain but have no effect on the structure of the cartilage.
Comparison table
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Potentially effective, yet temporary and delayed relief
The effectiveness of an injection varies depending on the product used and the stage of joint damage:
- Corticosteroids provide rapid relief, felt within a few days, but the effect generally wears off after four to six weeks.
- Hyaluronic acid acts more slowly, with noticeable improvement after several weeks, but effects that can last for several months.
- Effectiveness tends to decrease as joint damage becomes more advanced.
The French Society of Rheumatology recommends not exceeding 3 to 4 corticosteroid injections per year in the same joint. It advises against repeating hyaluronic acid injections if the initial injections have had no effect.
Reduced risks, to be monitored in the following days
Like any invasive procedure, knee injections carry risks. These remain limited when aseptic conditions are maintained.
- Post-injection reaction : a temporary increase in pain within 24 to 48 hours following the injection, which then subsides spontaneously.
- Joint infection (septic arthritis) : this is the most serious complication, but it remains rare (1 case per 50,000 procedures according to the French Society of Rheumatology). It manifests as intense pain, marked swelling, local heat, and sometimes fever, and requires an emergency consultation.
- Side effects related to corticosteroids, such as a temporary rise in blood sugar levels in diabetic patients.
- A hematoma at the puncture site, which is not particularly serious.
It is recommended to keep the knee relatively rested for 48 hours after the injection. Walking is still possible in reasonable amounts.
Before or after an injection, a second opinion for peace of mind
Knee injections are part of a more comprehensive care plan. Depending on the cause of your pain, several options may be considered, and their expected benefits can vary from person to person.
A second opinion can help clarify things when:
- an injection is recommended and you want to better understand its purpose, expected benefits, and limitations in your specific situation;
- several types of injections (corticosteroids, hyaluronic acid, or PRP) are being discussed and you want to understand the differences between them;
- an injection is being considered to delay surgery;
- pain persists after an initial round of injections;
- multiple causes could explain your symptoms, making the choice of treatment more complex.
In these situations, a second opinion provides an additional perspective to help you better understand your treatment options and move forward with confidence. It does not call your doctor's opinion into question; it complements it.
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Source
- French Society of Rheumatology, Knee Osteoarthritis: Recommendations from the French Society of Rheumatology (Sellam et al., 2020)
- Osteoarticular corticosteroid injections: Recommendations from the French Society of Rheumatology (Maugars et al., 2023)
- Ameli.fr, Knee osteoarthritis (gonarthrosis)
- Ameli.fr, Treatment of knee osteoarthritis
- INSERM, Osteoarthritis dossier
- Rhumatos.fr Review, What is its role in knee osteoarthritis? (Louati, Eymard, 2024)
- Neurosurgery, Platelet-rich plasma (PRP) and disc lesions: a literature review
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Did you know?
Have you been offered surgery?
Have you been offered surgery?
Surgery is never trivial. A medical specialist will analyze your file to confirm the recommendation or explore other therapeutic options.
Is there an alternative to surgery?
Is there an alternative to surgery?
A surgeon specializing in your condition will re-evaluate your file to confirm if surgery is necessary or to identify less invasive solutions.
Have you been presented with several treatment options?
Have you been presented with several treatment options?
Have you been presented with several treatment options?
An expert physician will analyze your medical records and history to help you choose the most appropriate strategy for your situation, whether it be medical treatment, surgery, or monitoring.
Torn between two treatments?
Torn between two treatments?
A specialist will explain exactly what each option entails, including effectiveness, side effects, and daily impact, so you can make your decision with confidence.
Still unsure about your diagnosis?
Still unsure about your diagnosis?
Still unsure about your diagnosis?
A specialist doctor will analyze your complete file (tests, imaging, medical history) to provide you with a reasoned diagnosis and guide your care.
Have you just received a diagnosis?
Have you just received a diagnosis?
Have you just received a diagnosis?
Have your medical file reviewed by a specialist in your condition. You will receive an additional opinion in less than 7 days, helping you move forward with clarity.
Is your condition rare or complex?
Is your condition rare or complex?
Diagdoor gives you access to a doctor who specializes in your condition to confirm your treatment plan, no matter where you live.
When facing cancer or a serious illness, every decision counts.
When facing cancer or a serious illness, every decision counts.
A doctor at an expert center will review your file to confirm your care plan, clarify the available options, and help you make decisions with confidence.
Have you received a diagnosis or been offered a treatment plan?
Have you received a diagnosis or been offered a treatment plan?
Have you received a diagnosis or been offered a treatment plan?
Submit your file in just a few minutes and get an expert opinion in under 7 days.
Have you received a diagnosis or been offered a treatment plan?
Submit your file in just a few minutes and get an expert opinion in under 7 days.
What is a medical second opinion?
What is a medical second opinion?
Following a diagnosis or a proposed treatment plan, a medical specialist can analyze your file and provide an additional perspective.
Your health insurance may cover your second opinion.
Your health insurance may cover your second opinion.
Many partner health insurance providers cover the Diagdoor service with no upfront costs. Check your eligibility as soon as you create your account.
Are you looking for a second opinion for a loved one?
Are you looking for a second opinion for a loved one?
The process is entirely online. Upload your available medical documents, and our team will take care of the rest.
How does a second opinion work on Diagdoor?
How does a second opinion work on Diagdoor?
Upload your medical documents online; our team will review your file within 48 hours, and an expert will provide their opinion in less than 7 days. Simple, secure, 100% online.
Not sure if your case is eligible?
Not sure if your case is eligible?
Our medical team can guide you before you submit your request. Describe your situation, and we will help you determine if Diagdoor can be of assistance.
Need the opinion of a
orthopedic surgeon
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orthopedic surgeon
Upload your file to Diagdoor. A
orthopedic surgeon
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