If you have knee pain from osteoarthritis and have been recommended an injection, you probably have many questions: which one is best? Will it hurt? How many can I get? Could they damage my knee? In this article, I explain with updated scientific evidence the differences between the three main options — corticosteroids, hyaluronic acid, and PRP — so you and your doctor can make the best decision.
What is a joint injection?
A joint injection delivers medication directly inside the knee joint. Think of it as bringing treatment exactly where it is needed most, without having to pass through the entire body. It is performed with a thin needle, in the office, and the procedure takes less than one minute.
Corticosteroids: fast relief, strategic use
Corticosteroid injections (commonly betamethasone in Latin America) combine a fast-acting form for immediate relief and a depot form for sustained anti-inflammatory effect over weeks.
How well do they work? Corticosteroids often produce clinically significant short-term pain relief, but the benefit is usually temporary and not a long-term disease-modifying strategy. Corticosteroids are excellent for calming acute inflammatory flares, but are not a medium or long-term solution.
How many can I get? Frequency is individualized according to diagnosis, prior response, and the risks of repeated use. There is no automatic number that applies to every patient.
Important note on corticosteroid injections
The AAOS conditionally recommends corticosteroids for knee OA. Their strength is rapid relief of acute flares. Their weakness: the effect lasts only 2-6 weeks and frequent use may deteriorate cartilage. Use them strategically, not as chronic treatment.
Hyaluronic acid: an option for symptom relief
Hyaluronic acid may be considered for symptom relief in selected patients. Response and duration vary, and cartilage protection or delayed progression should not be assumed.
What may be expected from hyaluronic acid
Pain reduction: hyaluronic acid can improve pain and stiffness for a limited period in selected patients. Reviews of the literature report mixed but often favorable short-term results effects on pain and function.
Effect on cartilage: protection or slower progression should not be promised. The clinical goal is symptom management and response is assessed individually.
Time to possible surgery: some observational series describe patients postponing knee replacement after hyaluronic acid. This does not prove that injections caused the delay or predict an individual timeline; the decision depends on symptoms, function, progression, and preferences.
Molecular weight matters: high molecular weight (HMW) formulations are often preferred in practice, although individual response varies and not all products are equivalent.
Why hyaluronic acid deserves more credit than it gets
The AAOS does not routinely recommend it, but the EUROVISCO 2025 consensus — an expert panel from 7 European countries — does support its use in specific clinical scenarios. It may be considered in selected clinical scenarios without assuming superiority, cartilage protection, or a guaranteed delay of knee replacement.
PRP: an option requiring individualized selection
Platelet-rich plasma (PRP) is prepared from the patient's own blood and injected into the joint. It may be considered in selected patients; outcomes depend on the product, protocol, diagnosis, and follow-up.
PRP can be a useful option in selected osteoarthritis. Comparisons with corticosteroids and hyaluronic acid vary by protocol, outcome, and follow-up, so treatment choice should be individualized.
The ESSKA-ICRS 2024 consensus granted PRP a Grade A recommendation for mild-to-moderate osteoarthritis (Kellgren-Lawrence grades I-III). The recommendation must be interpreted according to the clinical scenario, product, and individual characteristics.
Comparative table: three injections head to head
| Parameter | Corticosteroid | Hyaluronic Acid | PRP |
|---|---|---|---|
| Guidance range for onset | 1-2 weeks | 2-6 weeks | 2-4 weeks |
| Guidance range for duration | 2-6 weeks | 4-6 months | 6-12 months |
| Protocol | 1 injection; individualized frequency | 1 injection every 6-12 months | 3 sessions every 1-2 weeks |
| Effect on cartilage | Potential damage with frequent use | Protection cannot be assumed | Risks and evidence vary by product and protocol |
| Delays surgery? | Not demonstrated | Possible in some patients; not guaranteed | Not directly evaluated |
| Potential role | Acute inflammatory flares | Selected patients seeking symptom management | Selected cases after individualized assessment |
| Ideal KL grades | I-II (flares) | I-III | I-III |
| Society endorsement | AAOS: conditional | EUROVISCO 2025: yes (with conditions) | ESSKA 2024: Grade A (KL I-III) |
| Relative cost | Low | Moderate | High |
The therapeutic ladder: what to use based on your OA grade
Stepwise approach for knee osteoarthritis
When are injections no longer enough?
Persistent pain >6/10
Despite 2+ complete injection courses in the last 12 months.
Severe functional limitation
Unable to walk more than 500 meters, climb stairs, or perform daily activities.
Grade IV OA on X-ray
Complete joint space loss with bone-on-bone contact. Injections have minimal yield.
For more information on which therapies actually repair cartilage and which don't, read our article on cartilage repair: myths and truths.
Looking for exercises for this condition?
We have step-by-step rehabilitation guides with illustrated exercises and evidence-based protocols.
View guide: Grade IV Osteoarthritis →View guide: Chondromalacia →
Frequently asked questions
Does a knee injection hurt?
Most patients describe mild, brief discomfort during application. Local anesthetic is used and ultrasound-guided technique improves precision and reduces pain. The entire procedure takes less than one minute.
How many corticosteroid injections can I get per year?
Corticosteroid injection frequency is individualized according to diagnosis, prior response, and the risks of repeated use; injections should not be repeated automatically.
Can hyaluronic acid delay knee replacement surgery?
Yes. A study with data from thousands of patients showed that some patients treated with hyaluronic acid delay the decision for knee replacement, but this is not guaranteed and depends on many individual factors.
Can hyaluronic acid and PRP be combined?
Yes. Combining hyaluronic acid with PRP may be considered in selected cases, but response varies and superiority cannot be assumed for every patient.
How long do knee injections take to work?
As guidance ranges, corticosteroids may act in 1-2 weeks, hyaluronic acid in 2-6 weeks, and PRP in 2-4 weeks. Onset and progression vary by patient, product, and diagnosis.
When should treatment be reassessed and surgical options discussed?
When pain persists above 6/10 despite 2 or more injection courses, functional limitation is severe, or X-rays show grade IV osteoarthritis, it is time to evaluate surgical options such as arthroscopy, osteotomy, or knee replacement.
Not sure which injection is right for you?
A clinical evaluation with X-rays can determine your osteoarthritis grade and the best treatment for your case — with no generic prescriptions.
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