Synvisc and Synvisc-One are among the most recognisable viscosupplementation products in orthopaedic medicine. Manufactured by Sanofi Biosurgery (a Genzyme company), both products contain Hylan G-F 20 — a cross-linked derivative of hyaluronic acid engineered to closely mimic the viscoelastic properties of healthy synovial fluid. This guide gives practitioners a complete reference for Synvisc injections: formulation, mechanism of action, dosing schedules, technique, side effects, and a clinical comparison against other viscosupplements.

What Is Synvisc?

Synvisc is an intra-articular injection for the symptomatic treatment of pain caused by osteoarthritis (OA) of the knee. Its active ingredient, Hylan G-F 20, is produced by cross-linking sodium hyaluronate derived from avian sources (rooster comb). The cross-linking process creates a more durable, elastic gel that stays in the joint longer than non-cross-linked HA products and provides superior biomechanical performance.

Two formulations are available:

  • Synvisc (Hylan G-F 20): Three injections of 2 ml each, administered at weekly intervals.
  • Synvisc-One: A single-injection formulation delivering 6 ml of Hylan G-F 20 in one visit.

Licensed practitioners can order Synvisc products at wholesale prices through Bioresus.

Key Product Specifications

  • Active ingredient: Hylan G-F 20 (cross-linked HA derivative)
  • HA concentration: 8 mg/ml
  • Synvisc: 3 x 2 ml injections (weekly intervals) | Total: 6 ml
  • Synvisc-One: 1 x 6 ml single injection
  • Molecular weight: Hylan A ~6,000 kDa; Hylan B (cross-linked gel fraction)
  • Origin: Avian (rooster comb derived)
  • Regulatory status: FDA-cleared (US)

How Does Synvisc Work?

In knee OA, the concentration and molecular weight of native HA in synovial fluid decline significantly. This degrades the fluid’s lubricating and shock-absorbing properties, increasing cartilage wear and joint pain. Synvisc addresses this directly through several mechanisms:

  • Viscosupplementation: Hylan G-F 20 supplements depleted synovial fluid, restoring lubrication and load distribution across the joint.
  • Chondroprotection: Reduced mechanical stress on cartilage surfaces may slow degenerative progression.
  • Anti-inflammatory effects: Interaction with synoviocyte surface receptors modulates pro-inflammatory cytokine activity within the joint space.
  • Endogenous HA stimulation: Synvisc may prompt synoviocytes to upregulate native HA production over time.
  • Analgesic effects: Lower joint friction and reduced inflammatory load directly decrease nociceptor activation in the joint capsule.

The cross-linked structure of Hylan G-F 20 gives Synvisc substantially longer residence time in the joint compared to non-cross-linked HA products. Clinical benefits typically extend to 6 months, which is why Synvisc has maintained relevance alongside newer single-injection non-animal alternatives.

Indications for Synvisc Injection

Synvisc and Synvisc-One are FDA-cleared for the treatment of pain in knee osteoarthritis in patients who have failed conservative non-pharmacological therapy and simple analgesics. Appropriate candidates include:

  • Adults with Kellgren-Lawrence Grade II or III knee osteoarthritis confirmed on imaging
  • Patients who have not achieved adequate pain relief from physiotherapy, weight management, and oral analgesics
  • Active patients and athletes who need to maintain functional capacity
  • Patients seeking to delay or avoid total knee replacement surgery
  • Those requiring a non-opioid pain management option

Synvisc-One is particularly suited to patients for whom repeated clinic visits are a barrier. The single-injection format eliminates the scheduling burden of a multi-injection course. For practices stocking a full viscosupplementation portfolio, Synvisc-One sits alongside the orthopaedic injectable range as the premium convenience option for eligible patients.

Contraindications

  • Known hypersensitivity to hyaluronan preparations or any component of the formulation
  • Known allergy to avian proteins, feathers, or egg products — Synvisc is derived from rooster comb and is contraindicated in these patients
  • Active infection or skin disease at or near the injection site
  • Active intra-articular infection or significant joint inflammation at the time of injection
  • Venous or lymphatic stasis in the affected limb
  • Pregnancy and breastfeeding (insufficient safety data)

Avian origin is the single most important contraindication to screen for before prescribing Synvisc. All patients should be asked specifically about bird and egg allergies at consultation. Where allergy is confirmed or suspected, non-animal-sourced alternatives such as Orthovisc, Monovisc, or Durolane are the appropriate clinical choice.

Synvisc Dosage and Treatment Schedule

Synvisc (3-Injection Protocol)

  • Three injections of 2 ml each, administered at weekly intervals
  • Total dose: 6 ml Hylan G-F 20 delivered over three weeks
  • Re-treatment may be considered 6 months after the initial course based on clinical response

Synvisc-One (Single-Injection Protocol)

  • Single injection of 6 ml Hylan G-F 20 into the affected knee
  • Equivalent total dose to the 3-injection Synvisc course, delivered in one visit
  • Re-treatment at 6 months as clinically appropriate

In everyday clinical practice, Synvisc-One has largely replaced the 3-injection protocol for most patients. Equivalent efficacy with a single visit significantly improves compliance and practice throughput. The 3-injection formulation retains value in cases where a graduated dose approach is preferred or where clinical reassessment between sessions is a priority.

Synvisc Injection Technique

Equipment Required

  • Synvisc or Synvisc-One prefilled syringe (allow to reach room temperature before injection)
  • 21-gauge needle (not supplied; attach at time of administration)
  • Sterile gloves and draping
  • Antiseptic skin preparation
  • Optional: 1% lidocaine for local anaesthesia
  • Ultrasound machine (strongly recommended)

Injection Approaches

Superolateral approach (most common): Patient supine with knee fully extended. Insert the needle superior and lateral to the patella, directing medially and slightly inferiorly into the joint space. Aspirate any significant effusion before injecting. Inject slowly with minimal resistance.

Anteromedial or anterolateral approach (knee flexed): Patient seated with knee at 90 degrees. Insert the needle adjacent to the patellar tendon, medially or laterally. Suitable for patients unable to achieve full knee extension.

Ultrasound guidance is strongly recommended for all intra-articular knee injections. Image-guided placement consistently demonstrates superior intra-articular accuracy compared to landmark-guided technique, particularly in patients with obesity or significant anatomical variation. For Synvisc-One, where the full 6 ml dose is delivered in a single pass, accurate placement is especially critical.

Managing Joint Effusion

If significant effusion is present, aspirate before delivering Synvisc. Injecting into a heavily effused joint dilutes the product and may reduce efficacy. A two-needle technique — using separate needles for aspiration and injection — maintains procedural sterility throughout.

Post-Injection Patient Instructions

  • Avoid strenuous activity, prolonged standing, and heavy lifting for 48 hours post-injection
  • Apply ice to the knee for 15-20 minutes to reduce immediate discomfort
  • Mild swelling, warmth, or stiffness for 24-72 hours is expected and self-limiting
  • Meaningful pain relief typically takes 4-8 weeks to become apparent; patients should not assess efficacy before this point

Synvisc Side Effects and Safety Profile

Common Local Reactions

  • Injection site pain (most frequently reported, typically mild and transient)
  • Swelling or joint effusion (usually resolves within 48-72 hours)
  • Warmth and redness around the knee
  • Temporary joint stiffness in the 24-48 hours immediately post-injection

Pseudoseptic Reaction

Synvisc has a documented, higher incidence of acute inflammatory (pseudoseptic) reactions compared to some other viscosupplements — notably those using non-cross-linked HA. This presents as sudden-onset pain, warmth, and joint effusion within 24-72 hours post-injection. The reaction is typically self-limiting but must be distinguished from septic arthritis, which requires urgent investigation. Advise all patients to contact the practice if joint pain increases significantly within 72 hours.

Management includes aspiration of excess effusion, NSAIDs, and rest. If septic arthritis cannot be excluded clinically, synovial fluid analysis is required.

Serious Complications (Rare)

  • Septic arthritis: Minimised with strict aseptic technique; urgent evaluation required if fever or rapidly worsening symptoms develop.
  • Hypersensitivity and allergic reactions: More likely with avian-sourced HA in sensitised patients. Practitioners should be equipped to manage anaphylaxis.

Expected Clinical Outcomes

Synvisc and Synvisc-One have an extensive published evidence base. Key outcomes from clinical trials include:

  • Significant reductions in pain VAS and WOMAC scores versus placebo, typically measurable from 4-6 weeks post-treatment
  • Clinical response sustained for up to 6 months in responding patients
  • Responder rates of approximately 60-70% in patients with mild-to-moderate OA
  • Head-to-head data demonstrates equivalent efficacy between Synvisc (3 injections) and Synvisc-One (single injection)
  • Outcomes are best in patients with Kellgren-Lawrence Grade II-III OA; Grade IV patients are unlikely to achieve meaningful benefit

Synvisc vs Other Viscosupplements

Selecting the right viscosupplement involves weighing patient profile, practice workflow, and clinical considerations:

Synvisc vs Durolane: Durolane is a single-injection, non-animal-sourced product that eliminates avian allergy risk entirely. Durolane uses non-cross-linked NASHA technology. Synvisc-One’s cross-linked Hylan G-F 20 may provide superior biomechanical viscosity in some patients, but Durolane is the safer first-line choice where avian allergy cannot be excluded.

Synvisc vs Monovisc: Monovisc is a single-injection, non-animal-sourced alternative that completely removes avian allergy risk. For practices where allergy screening is uncertain, Monovisc is a safer default.

Synvisc vs Orthovisc: Orthovisc is a 3-4 injection, non-animal-sourced product. Neither requires multiple visits like the 3-injection Synvisc protocol, but Orthovisc eliminates avian allergy risk entirely.

Synvisc vs Supartz FX: Both are avian-derived. Supartz FX requires 5 injections versus Synvisc-One’s single injection — a significant practical disadvantage. Where a single-injection avian-derived option is appropriate, Synvisc-One is the more convenient choice.

Patient Selection and Counselling

Ideal Candidates

  • Kellgren-Lawrence Grade II-III knee OA confirmed on imaging
  • No bird or egg allergy (mandatory pre-treatment screening)
  • Non-responders to conservative management after an adequate trial
  • Patients who prefer a single-visit treatment (Synvisc-One)
  • Active individuals who need sustained functional improvement

Key Counselling Points

  • Pain relief takes 4-8 weeks to onset; do not assess efficacy before this period
  • Synvisc provides symptomatic relief only, not disease modification
  • Non-response occurs in approximately 30-40% of patients; set realistic expectations
  • Avian allergy screening is mandatory before prescribing
  • Pseudoseptic reactions are possible; patients should contact the clinic immediately if pain increases sharply within 72 hours post-injection

Ordering Synvisc Wholesale

Licensed practitioners can order Synvisc 2 ml and Synvisc-One 6 ml at wholesale prices through Bioresus. All products are sourced from authorised distributors and shipped to maintain cold chain integrity. Browse the full orthopaedic injectable range including Durolane, Orthovisc, and Monovisc for a complete viscosupplementation offering.

Conclusion

Synvisc and Synvisc-One offer a well-evidenced viscosupplementation option with a long clinical track record. The cross-linked Hylan G-F 20 formulation provides durable joint lubrication, and Synvisc-One’s single-injection protocol directly addresses the compliance challenge that hampers multi-injection regimens. The main clinical decision point is avian allergy screening: Synvisc is appropriate for allergy-screened patients, while non-animal-sourced products remain the safer default where screening is uncertain.

When used in properly selected patients, Synvisc delivers meaningful, sustained knee pain relief that supports patient function and quality of life — and, for many, provides the bridge between conservative management and surgical intervention.