Understanding HA Injection Options
If your doctor has recommended hyaluronic acid (HA) injections for knee osteoarthritis, you may have heard of different brand names. Synvisc-One and Euflexxa are two of the most commonly prescribed options—but they have important differences.
Both work by restoring lubrication and cushioning to your knee joint, but they differ in molecular structure, source material, and how they’re administered.
Side-by-Side Comparison
| Factor | Synvisc-One | Euflexxa |
|---|---|---|
| Injections needed | 1 | 3 (weekly) |
| Molecular weight | High (6 million Da) | Low-medium (2.4-3.6 million Da) |
| Source | Avian (chicken comb) | Bacterial fermentation |
| Volume | 6 mL single injection | 2 mL × 3 injections |
| Egg allergy safe | No | Yes |
| Cross-linking | Yes (hylan polymer) | No (native HA) |
| Duration of relief | Up to 6 months | Up to 6 months |
| Medicare covered | Yes | Yes |
| Manufacturer | Sanofi | Ferring |
Synvisc-One: Single-Injection Convenience
What It Is
Synvisc-One is a high molecular weight, cross-linked hyaluronic acid (called hylan G-F 20) derived from chicken combs. The cross-linking process creates a gel-like substance that provides significant cushioning.
Advantages
Considerations
Best For
- Patients wanting minimal appointments
- Those with no avian allergies
- Anyone with scheduling constraints (travel, work)
- Patients who’ve responded well to Synvisc (original three-injection) formulation
Euflexxa: Non-Avian Alternative
What It Is
Euflexxa contains native (non-cross-linked) hyaluronic acid produced through bacterial fermentation. This means it’s not derived from any animal source, making it suitable for patients with egg or poultry allergies.
Advantages
Considerations
Best For
- Patients with egg or poultry allergies
- Those who prefer smaller injection volumes
- Patients who’ve had reactions to avian-derived HA
- Anyone who can easily attend three weekly appointments
The Science: Molecular Weight Matters?
The Debate
There’s ongoing discussion about whether high molecular weight (HMW) or low-medium molecular weight (LMW) HA works better:
High MW Theory (Synvisc):
- More viscous = better cushioning
- Longer residence time in joint
- Better shock absorption
Low-Medium MW Theory (Euflexxa):
- Better tissue penetration
- More similar to natural HA
- Less inflammatory response
What Research Shows
Clinical studies comparing different HA products have found:
- Similar efficacy across most molecular weights
- Duration of effect comparable (both ~6 months)
- No clear winner in head-to-head trials
- Individual variation - some patients respond better to one than the other
Bottom line: Both work. The “best” choice often comes down to practical factors like allergies, scheduling, and insurance coverage.
Allergy Considerations
Important: Avian Allergies
If you have allergies to:
- Eggs
- Chicken
- Feathers
- Other poultry products
You should avoid Synvisc-One (and original Synvisc) and choose a non-avian alternative like Euflexxa.
Always inform your doctor about any allergies before receiving HA injections.
Insurance and Cost Comparison
Medicare Coverage
Both Synvisc-One and Euflexxa are covered by Medicare Part B when medically necessary criteria are met:
- Documented knee osteoarthritis
- Failed conservative treatment (3+ months)
- Meets Local Coverage Determination (LCD) requirements
Cost Factors
| Factor | Synvisc-One | Euflexxa |
|---|---|---|
| Office visits | 1 | 3 |
| Copays (typical) | 1 × $50-150 | 3 × $20-50 |
| Injection fees | Once | Three times |
| Total out-of-pocket | Similar | Similar |
Note: Actual costs vary by insurance plan, deductible status, and provider billing.
Other HA Products to Know
Synvisc-One and Euflexxa aren’t your only options. Other FDA-approved HA products include:
Single-Injection Products
| Product | Source | Molecular Weight |
|---|---|---|
| Synvisc-One | Avian | High |
| Monovisc | Avian | High |
| Durolane | Bacterial | Medium |
| Gel-One | Avian | High |
Multi-Injection Products
| Product | Injections | Source |
|---|---|---|
| Euflexxa | 3 weekly | Bacterial |
| Supartz FX | 3-5 weekly | Avian |
| Hyalgan | 3-5 weekly | Avian |
| Orthovisc | 3-4 weekly | Avian |
Making Your Decision
Questions to Ask Your Doctor
- Do I have any allergies that would rule out certain products?
- What product do you have the most experience with?
- How many appointments can I realistically attend?
- What does my insurance cover?
- Have you seen different results with different products?
Decision Framework
Choose Synvisc-One if:
- You want one appointment
- You have no avian allergies
- Scheduling multiple visits is difficult
- Your provider recommends it based on experience
Choose Euflexxa if:
- You have egg/chicken allergies
- You prefer smaller injection volumes
- You can easily attend three appointments
- You’ve had reactions to avian-derived products
The Bottom Line
Both Products Work
Synvisc-One and Euflexxa are both effective treatments for knee osteoarthritis:
- Clinical efficacy is similar
- Duration of relief is comparable (~6 months)
- Both are covered by Medicare
- Both have good safety profiles
The choice often comes down to:
- Allergy status (avian vs. non-avian)
- Scheduling preference (1 vs. 3 visits)
- Insurance coverage specifics
- Your doctor’s experience and recommendation
Don’t overthink it—the best HA product is one that fits your situation and that you’ll actually use.
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How to Choose a ProviderReferences
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Synvisc-One (hylan G-F 20) Prescribing Information. Sanofi.
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Euflexxa (sodium hyaluronate) Prescribing Information. Ferring Pharmaceuticals.
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Comprehensive review of viscosupplementation in osteoarthritis. Orthopedic Reviews. Full Text
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Comparison of high and low molecular weight hyaluronic acid. PMC. PMC8567800
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CMS LCD L39529 - Intraarticular Knee Injections. Medicare Coverage Database
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