Synvisc / Synvisc-One Side Effects: What to Expect
Synvisc / Synvisc-One side effects and safety guide. Common reactions, when to worry, avian allergy considerations, and what to expect after your injection.
By Joint Pain Authority Team
Quick Answer
Synvisc / Synvisc-One is generally well-tolerated. The most common side effect is temporary pain or swelling at the injection site, which typically resolves within 1-3 days. Serious side effects are rare. Important: Synvisc / Synvisc-One is derived from rooster combs — tell your doctor if you have avian (bird/egg/feather) allergies.
About Synvisc / Synvisc-One
- Active ingredient: Hylan G-F 20 (rooster-comb derived)
- Dosing: 3 injections (Synvisc) or 1 injection (Synvisc-One)
- FDA-approved for: Knee osteoarthritis pain
Common Side Effects
- Joint pain or swelling at injection site (most common, 10-15%)
- Warmth or redness around the knee
- Fluid buildup in the joint
- Itching or rash at injection site
- Headache
- Rare: pseudoseptic reaction (severe swelling within 48 hours, occurs in ~2-3% of patients)
Most side effects are mild and temporary, resolving within 1-3 days without treatment. Applying ice and resting the knee can help.
When to Call Your Doctor
Contact your doctor if you experience:
- Severe swelling that develops within 24-48 hours of injection
- Fever (temperature over 101°F / 38.3°C)
- Increasing redness or warmth spreading beyond the injection site
- Drainage from the injection site
- Pain that gets significantly WORSE after the first 48 hours
Managing Side Effects
| Side Effect | What to Do |
|---|---|
| Mild pain/soreness | Ice for 20 min on/off, OTC acetaminophen |
| Swelling | Elevate leg, ice, rest for 24-48 hours |
| Stiffness | Gentle range-of-motion exercises after 24 hours |
| Bruising | Normal — resolves on its own in 3-7 days |
Avian Allergy Considerations
Synvisc / Synvisc-One is derived from rooster combs. If you have known allergies to birds, feathers, eggs, or poultry products, tell your doctor before receiving this injection. Your doctor may recommend a non-avian alternative such as Euflexxa or Durolane instead.
How Synvisc / Synvisc-One Compares on Safety
The ESSKA 2025 meta-analysis of 76,061 patients found that hyaluronic acid injections have an overall adverse event rate of approximately 8.7% — significantly lower than cortisone injections (11.0%). Synvisc / Synvisc-One falls within this safety profile.
Frequently Asked Questions
Are Synvisc / Synvisc-One side effects worse than cortisone?
No. HA injections like Synvisc / Synvisc-One generally have fewer systemic side effects than cortisone. Cortisone can cause blood sugar spikes, facial flushing, and with repeated use, cartilage damage. Synvisc / Synvisc-One’s side effects are mostly local and temporary.
How long do side effects last?
Most side effects resolve within 1-3 days. If you’re still experiencing significant symptoms after 5-7 days, contact your doctor.
Can I take ibuprofen for injection site pain?
Ask your doctor first. Many providers recommend acetaminophen (Tylenol) over NSAIDs for the first 48 hours after injection, as NSAIDs may theoretically affect the hyaluronic acid.
Will the side effects be worse with my second series?
Not typically. Some patients actually experience fewer side effects with subsequent injection series as their body adjusts.
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