What Are the 3 Injections for Knee Pain? Cortisone, Gel, and PRP Compared

Q: How many knee injections can you get per year?

Cortisone: maximum 3–4 per year per joint (at least 3 months between injections). Hyaluronic acid gel: typically every 6 months, or twice per year. PRP: varies by protocol, often 1–3 initial injections followed by annual maintenance. Your doctor will determine the appropriate frequency based on your response and condition.

Q: What injection works fastest for knee pain?

Cortisone works fastest, typically providing relief within 1–3 days. Hyaluronic acid injections are slower — most patients notice gradual improvement starting at 2–4 weeks, with full benefit by 4–8 weeks. PRP is also gradual, with typical onset at 4–8 weeks. --- ---

Key Takeaways

The 3 main knee pain injections are cortisone (corticosteroid), hyaluronic acid (gel/viscosupplementation), and PRP (platelet-rich plasma)
Cortisone provides the fastest relief (days) but wears off in 1–6 weeks and may damage cartilage with repeated use
Hyaluronic acid gel injections last 6–12 months and are covered by Medicare Part B — the only long-duration option with reliable insurance coverage
PRP shows the best long-term outcomes in recent studies but is not covered by Medicare or most insurance plans
The right injection depends on your arthritis severity, insurance coverage, and treatment goals
Most patients try treatments in sequence: cortisone first for acute flares, then gel injections for ongoing management, and PRP if other options fail

If you’re researching injections for knee arthritis, you’ll quickly discover three options come up repeatedly: cortisone shots, gel injections, and PRP. But what exactly are these treatments, and how do they compare?

The 3 main injections for knee pain are:

Cortisone (corticosteroid) injections — fast-acting anti-inflammatory shots
Hyaluronic acid (gel/viscosupplementation) injections — lubrication-restoring gel shots
PRP (platelet-rich plasma) injections — growth factor injections made from your own blood

Each works differently, lasts a different amount of time, carries different costs, and has a different insurance coverage profile. This guide breaks down everything you need to make an informed decision with your doctor.

Injection #1: Cortisone (Corticosteroid) Injections

What Are Cortisone Injections?

Cortisone injections deliver a synthetic steroid directly into your knee joint. Steroids are powerful anti-inflammatory agents — they rapidly reduce swelling, inflammation, and pain.

Cortisone: Quick Facts


How it works	Reduces inflammation in the joint
Onset of relief	1–3 days
Duration	1–6 weeks typically; rarely 3 months
Medicare coverage	Yes, covered
Self-pay cost	$100–$300 per injection
Cartilage impact	May damage cartilage with repeated use
How often	Maximum 3–4 times per year per joint

How Cortisone Works

Your arthritic knee produces excess inflammatory chemicals that cause pain and swelling. Cortisone blocks this inflammatory cascade quickly and powerfully. That’s why many patients feel relief within 24–72 hours — faster than any other knee injection.

The Limitation: Short Relief and Cartilage Concerns

The relief is real, but temporary. Most patients experience pain reduction for 1 to 6 weeks, with the average around 4–6 weeks. A landmark 2019 study in JAMA found that patients receiving multiple cortisone injections had a 57% higher risk of eventually needing knee replacement compared to those receiving hyaluronic acid injections.

Important Cartilage Warning

Research shows that repeated cortisone injections can accelerate cartilage breakdown. Most guidelines recommend no more than 3–4 injections per year per joint and at least 3 months between injections. Cortisone is most appropriate for acute flares, not long-term ongoing management.

Who Cortisone Is Best For

Acute flares of knee arthritis with significant swelling
Short-term relief before a planned event or trip
Patients who need to reduce inflammation quickly before starting physical therapy
Occasional use when other treatments aren’t available

Medicare coverage: Yes. Cortisone injections are covered by Medicare Part B and most private insurance plans with no prior authorization required in most cases.

Injection #2: Hyaluronic Acid (Gel) Injections

What Are Gel Injections?

Hyaluronic acid (HA) injections — also called gel injections, viscosupplementation, or hyaluronate injections — deliver a gel-like substance directly into your knee joint. This gel replaces and supplements the natural joint fluid that breaks down in osteoarthritis.

Hyaluronic Acid Gel: Quick Facts


How it works	Restores joint lubrication and cushioning
Onset of relief	2–8 weeks (gradual)
Duration	6–12 months
Medicare coverage	Yes, covered under Part B
Self-pay cost	$500–$1,500 per course
Cartilage impact	None — may be protective
How often	Every 6 months when effective

How Gel Injections Work

Your joint fluid (synovial fluid) contains hyaluronic acid that provides natural lubrication and shock absorption. In arthritic joints, this fluid becomes thin and watery — less effective at protecting the joint surfaces. Gel injections restore this cushioning function.

Unlike cortisone, gel injections don’t just mask inflammation. They address the underlying mechanical problem — reduced joint fluid quality — which is why relief lasts much longer.

The Evidence

The FDA first approved hyaluronic acid injections in 1997, and they’ve been covered by Medicare ever since. Clinical studies show:

70–80% of patients experience meaningful pain reduction
Average pain improvement of 51% in meta-analyses
Relief lasting an average of 6 months, often 9–12 months
Research following 182,000 patients found that each additional course of gel injections extended the time before knee replacement by months to years

According to a 2024 meta-analysis of 9,338 knees, hyaluronic acid injections provide significant pain and function improvement compared to placebo, with a favorable long-term safety profile.

No Cartilage Damage Risk

This is a key advantage over cortisone. Research shows hyaluronic acid is neutral to protective for cartilage — it does not accelerate joint damage. Patients can receive gel injections every six months without concerns about worsening their arthritis.

Who Gel Injections Are Best For

Medicare beneficiaries seeking long-lasting, covered treatment
Patients who’ve tried cortisone but want longer-lasting results
Anyone who wants to delay or avoid knee replacement surgery
Patients with mild to moderate knee osteoarthritis (not severe bone-on-bone)

Medicare coverage: Yes. Medicare Part B covers hyaluronic acid injections for knee osteoarthritis when medical necessity criteria are met. Patients typically pay 20% coinsurance after their Part B deductible.

Injection #3: PRP (Platelet-Rich Plasma) Injections

What Are PRP Injections?

PRP injections use your own blood, concentrated to separate growth factors and platelets, which are then injected back into your knee joint. These growth factors may stimulate tissue repair, reduce inflammation, and improve joint function.

PRP: Quick Facts


How it works	Growth factors from your own blood promote healing
Onset of relief	4–8 weeks
Duration	6–12 months (some studies show longer)
Medicare coverage	No — not covered
Self-pay cost	$500–$2,000 per treatment
Cartilage impact	May be regenerative (early research)
How often	Variable; typically 1–3 injections

How PRP Works

A small amount of your blood is drawn and spun in a centrifuge to concentrate platelets and growth factors. This platelet-rich concentrate is then injected into your knee joint. The growth factors may signal your body to reduce inflammation and stimulate repair processes in the joint tissue.

Growing Evidence — But Significant Limitations

PRP research has accelerated significantly. A 2025 network meta-analysis ranked PRP highest among knee injection options for long-term pain and function outcomes at 6–12 months. The 2024 ESSKA (European Society of Sports Traumatology) guidelines conditionally recommend PRP for patients with early-to-moderate knee osteoarthritis who have failed conservative treatments.

However, important limitations exist:

No standardized preparation — PRP products vary significantly between providers
Evidence gaps — fewer large, well-controlled studies compared to HA injections
No Medicare coverage — significant cost barrier for older adults
Less effective for severe arthritis — not recommended for Kellgren-Lawrence grade IV disease

Who PRP Is Best For

Patients willing to pay out-of-pocket for potentially superior long-term outcomes
Those who haven’t responded to cortisone or gel injections
Patients with early-to-moderate osteoarthritis (KL grades 1–3)
Athletes or active patients wanting to optimize joint health

Medicare coverage: No. PRP is considered investigational/experimental by Medicare and most private insurance plans. Some newer Medicare Advantage plans may have limited coverage — check your specific plan.

Side-by-Side Comparison: All 3 Knee Injections

Factor	Cortisone	Hyaluronic Acid (Gel)	PRP
Mechanism	Reduces inflammation	Restores lubrication	Stimulates repair with growth factors
Onset	1–3 days	2–8 weeks	4–8 weeks
Duration	1–6 weeks	6–12 months	6–12+ months
Medicare Coverage	✓ Yes	✓ Yes	✗ No
Self-Pay Cost	$100–$300	$500–$1,500	$500–$2,000
Evidence Level	Strong (short-term)	Moderate	Limited/Emerging
Cartilage Impact	Potentially harmful long-term	Neutral/Protective	Potentially regenerative
Repeat Safety	Limit to 3–4×/year	Every 6 months	Variable
Best For	Acute flares	Ongoing management	Failed other options

How to Choose the Right Knee Injection

There’s no single “best” injection for everyone. The right choice depends on your specific situation.

Decision Framework

Choose cortisone if you:

Need fast relief for an acute flare-up
Have significant swelling that needs to be brought down quickly
Need short-term relief before starting physical therapy
Are using it occasionally (not as a long-term strategy)

Choose hyaluronic acid (gel) injections if you:

Have Medicare and want covered, long-lasting relief
Want a treatment you can safely repeat every 6 months
Are focused on delaying or avoiding knee replacement
Have mild to moderate osteoarthritis
Had good results from cortisone but want longer-lasting relief

Choose PRP if you:

Are willing to pay out-of-pocket for potentially superior outcomes
Have not responded adequately to cortisone or gel injections
Have early-to-moderate osteoarthritis
Are looking for the most recent evidence-based option

In practice, most physicians follow a stepwise approach:

Conservative care first (physical therapy, weight management, OTC medications)
Cortisone for acute flares and to confirm the knee joint as the pain source
Hyaluronic acid gel injections for longer-lasting relief when cortisone wears off
PRP if gel injections don’t provide adequate relief and the patient can afford out-of-pocket costs
Surgery consultation when non-surgical options are exhausted

This sequence isn’t rigid — your doctor will individualize based on your X-ray findings, pain level, insurance coverage, and goals.

A Note on Imaging Guidance

Regardless of which injection type you choose, imaging guidance matters. Studies show that injections performed with fluoroscopic (X-ray) or ultrasound guidance reach the joint space accurately in 96–100% of cases, compared to up to a 30% miss rate without guidance. An injection that misses the joint space provides no benefit regardless of the medication used.

When evaluating providers, ask: “Do you use imaging guidance for knee injections?”

Frequently Asked Questions

What is the best knee injection for arthritis?

There’s no single best injection for all patients. PRP shows the strongest long-term outcomes in recent studies but isn’t covered by Medicare. Hyaluronic acid gel injections offer the best combination of long-lasting relief (6–12 months) and insurance coverage. Cortisone is best for short-term flare management. The right choice depends on your arthritis severity, goals, and insurance situation.

How long do knee injections last?

Duration varies significantly by type: cortisone typically lasts 1–6 weeks; hyaluronic acid gel injections last 6–12 months on average; PRP injections last 6–12 months or longer in some studies. Individual results vary based on arthritis severity, weight, activity level, and injection accuracy.

Are knee injections covered by Medicare?

Medicare Part B covers both cortisone and hyaluronic acid (gel) injections for knee osteoarthritis when medically necessary. PRP injections are not covered by Medicare, which is considered investigational. You’ll pay 20% coinsurance for covered injections after meeting your Part B deductible.

Can you get multiple types of knee injections?

Yes. Many patients receive different types at different times. A common pattern is cortisone for an acute flare, followed by hyaluronic acid injections for ongoing management. Doctors typically do not mix injection types simultaneously in the same joint — you’d wait for one to wear off before trying another.

How many knee injections can you get per year?

Cortisone: maximum 3–4 per year per joint (at least 3 months between injections). Hyaluronic acid gel: typically every 6 months, or twice per year. PRP: varies by protocol, often 1–3 initial injections followed by annual maintenance. Your doctor will determine the appropriate frequency based on your response and condition.

Which injection is safest for long-term use?

Hyaluronic acid gel injections have the strongest long-term safety record — FDA-approved since 1997 with no documented cartilage damage risk. They can be repeated every 6 months indefinitely. Cortisone has well-documented cartilage concerns with repeated use. PRP appears safe but lacks the decades of follow-up data that HA injections have.

What injection works fastest for knee pain?

Cortisone works fastest, typically providing relief within 1–3 days. Hyaluronic acid injections are slower — most patients notice gradual improvement starting at 2–4 weeks, with full benefit by 4–8 weeks. PRP is also gradual, with typical onset at 4–8 weeks.

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Last reviewed: March 2026

Medical Disclaimer: This article is for educational purposes only and does not constitute medical advice. Always consult your healthcare provider to determine which treatment is appropriate for your specific condition and circumstances.