What Are Hyaluronic Acid Injections?
Hyaluronic acid (HA) injections, also known as viscosupplementation or “gel shots,” are a non-surgical treatment for knee osteoarthritis. These injections restore the natural lubricating and cushioning properties of joint fluid that deteriorate with arthritis.
Hyaluronic acid is a naturally occurring substance in your body, found in high concentrations in joint fluid, skin, and eyes. In healthy joints, HA provides:
- Lubrication to reduce friction between cartilage surfaces
- Shock absorption to protect joints during movement
- Nutrient delivery to cartilage cells
In osteoarthritic joints, HA concentration and quality decrease, contributing to pain and stiffness. Viscosupplementation aims to restore these protective properties.
How Do HA Injections Work?
The exact mechanisms are still being studied, but HA injections appear to work through multiple pathways:
Immediate Effects
- Improved joint lubrication
- Enhanced shock absorption
- Reduced friction during movement
Longer-Term Effects
- Anti-inflammatory properties
- Stimulation of natural HA production
- Protection of remaining cartilage
- Pain receptor modulation
Who Is a Good Candidate?
HA injections work best for patients with:
- Mild to moderate knee osteoarthritis (Stages 2-3)
- Inadequate response to conservative treatments (PT, OTC medications)
- Desire to avoid or delay surgery
- No contraindications (joint infection, skin conditions at injection site)
Less Ideal Candidates
HA injections may be less effective for:
- Severe, bone-on-bone arthritis (Stage 4)
- Patients with inflammatory arthritis (rheumatoid arthritis)
- Those with unrealistic expectations of complete pain elimination
The Treatment Process
Before Your Injection
- Medical evaluation to confirm diagnosis and candidacy
- Insurance verification and prior authorization (if needed)
- Review of current medications (blood thinners may need adjustment)
- Discussion of expectations and treatment goals
During the Procedure
A typical HA injection appointment involves:
- Preparation: The injection site is cleaned and numbed with local anesthetic
- Imaging guidance: Fluoroscopy (real-time X-ray) ensures precise needle placement
- Fluid removal: Excess joint fluid may be aspirated before injection
- Injection: HA gel is slowly injected into the joint space
- Post-injection assessment: Range of motion is checked
Total procedure time: 15-30 minutes
After Your Injection
- First 24-48 hours: Rest and avoid strenuous activity
- Ice as needed: To reduce any temporary swelling
- Resume activities: Gradually return to normal activities
- Follow-up: Typically scheduled at 4-6 weeks to assess response
Why Imaging Guidance Matters
One of the most critical factors in HA injection success is accurate placement. Research shows:
- Blind injections miss the joint space in up to 30% of cases
- Fluoroscopic-guided injections achieve accurate placement in 96-100% of cases
- Accuracy directly correlates with treatment effectiveness
When choosing a provider, ask: “Do you use imaging guidance for injections?” This single factor can significantly impact your outcomes.
Available HA Brands
Several FDA-approved HA products are available, differing in:
- Molecular weight (affects duration of effect)
- Number of injections required per course
- Cross-linking (affects gel properties)
Single-Injection Options
| Brand | Duration |
|---|---|
| Synvisc-One | 6 months |
| Monovisc | 6 months |
| Durolane | 6 months |
| Gel-One | 6 months |
Multi-Injection Series
| Brand | Injections | Interval |
|---|---|---|
| Euflexxa | 3 | Weekly |
| Supartz FX | 5 | Weekly |
| Hyalgan | 3-5 | Weekly |
| Orthovisc | 3-4 | Weekly |
Your provider will recommend the most appropriate product based on your specific situation, insurance coverage, and preferences.
Expected Outcomes
Timeline of Results
- Weeks 1-2: Initial relief as inflammation subsides
- Weeks 4-8: Full benefit typically reached
- Months 6-12: Benefits may persist; repeat injections can maintain relief
Success Rates
Clinical studies show:
- 70-80% of patients experience meaningful pain reduction
- 50-60% achieve significant improvement in function
- Benefits typically last 6-12 months
- Repeat injections can be administered every 6 months if effective
Factors Affecting Success
Better outcomes are associated with:
- Earlier stage OA (not bone-on-bone)
- Accurate injection placement (imaging guidance)
- Combination with physical therapy
- Weight management
- Realistic expectations
Potential Side Effects
HA injections are generally well-tolerated. Common side effects include:
Common (Usually Resolve Within Days)
- Injection site pain or discomfort
- Mild swelling
- Warmth around the joint
- Temporary stiffness
Less Common
- Allergic reaction (rare; more common with avian-derived products)
- Infection (very rare with proper sterile technique)
- Joint effusion (excess fluid)
Report immediately: Fever, severe pain, significant swelling, or redness spreading from injection site.
Insurance Coverage
Medicare Coverage
Medicare Part B covers HA injections for knee osteoarthritis when:
- Diagnosis of knee OA is documented
- Conservative treatments have been tried (PT, medications)
- Medical necessity criteria are met
Patients typically pay 20% coinsurance after meeting their Part B deductible.
Medicare remains stable: Coverage has been consistent since 1997, making it a reliable option for eligible patients. Learn more about Medicare coverage →
Private Insurance
Most commercial plans cover HA injections with:
- Prior authorization (usually required)
- Step therapy requirements (may need to try other treatments first)
- Documentation of medical necessity
Coverage varies significantly by plan—verify before treatment.
Important Coverage Update
Some commercial insurers are reducing HA injection coverage. Notably, BCBS Illinois announced it will end coverage effective January 2026. If you have commercial insurance, verify your current coverage status before scheduling treatment.
HA Injections vs. Other Treatments
| Factor | HA Injections | Cortisone | PRP |
|---|---|---|---|
| Duration | 6-12 months | 6-12 weeks | Variable |
| Evidence | Moderate | Strong (short-term) | Limited |
| Medicare Coverage | Yes | Yes | No |
| Repeat Frequency | Every 6 months | 3-4x/year max | Variable |
| Cartilage Impact | Neutral/Protective | Potentially harmful long-term | Unknown |
Questions to Ask Your Provider
- Do you use fluoroscopic guidance for injections?
- Which HA brand do you recommend for my situation?
- What is the total cost after insurance?
- How many patients with my condition have you treated?
- What complementary treatments do you recommend?
- What are realistic expectations for my specific case?
Red Flags to Watch For
Be cautious of providers who:
- Don’t use imaging guidance for injections
- Guarantee specific outcomes
- Push unnecessary additional procedures
- Don’t verify insurance coverage upfront
- Rush through the consultation without proper evaluation
Related Resources
- Knee Osteoarthritis Guide
- HA Injections vs. Cortisone
- Medicare Coverage for Knee Injections
- BCBS Illinois Coverage Update — Important news for BCBS members
- How to Choose a Joint Pain Clinic