Knee Gel Injections (Viscosupplementation): What to Expect
Knee gel injections, also called hyaluronic acid injections or viscosupplementation, add a smooth, cushioning fluid back into an arthritic knee. By improving joint lubrication and shock absorption, many people notice easier movement and less pain with walking, stairs, and daily activities. Your clinician will assess your symptoms, imaging, and prior treatments to decide whether this low-risk option fits your goals and overall plan for knee osteoarthritis care.
What is knee gel injection (viscosupplementation)?
Knee gel injections are intra-articular hyaluronic acid (HA) treatments designed to supplement the joint’s natural synovial fluid, which thins with osteoarthritis. HA is a viscoelastic molecule that improves lubrication and shock absorption inside the knee, helping some people move with less pain.
In the United States, HA knee injections are FDA-cleared as medical devices to treat pain from knee osteoarthritis in patients who haven’t had adequate relief from conservative care. Current clearance applies to the knee only; use in other joints is off-label.
Clinical guidance varies: some guidelines are cautious about routine use because trial results are mixed, while others allow shared decision-making based on individual response, comorbidities, and goals. In practice, viscosupplementation is often considered after exercise therapy, weight management, oral/topical analgesics, bracing, and physical therapy.
Procedure Details
What should you try before knee gel injections?
Most people start with first-line care for knee osteoarthritis: targeted exercise and physical therapy, weight management, activity modification, heat/ice, oral or topical NSAIDs, and bracing as needed. If symptoms persist despite these measures, your clinician may discuss injections such as corticosteroids, platelet-rich plasma (PRP), or hyaluronic acid (viscosupplementation) as next-step options based on your goals and health profile.
What happens during the injection visit?
Your visit is typically an outpatient, office-based procedure that takes only a few minutes:
Your clinician cleans and sterilizes the skin over the knee.
Imaging guidance (ultrasound or fluoroscopy/X-ray) may be used to confirm accurate intra-articular placement.
Local anesthetic numbs the area.
If there is a large effusion, joint aspiration may be performed first to reduce pressure and improve accuracy.
Hyaluronic acid is injected into the knee joint space.
A small bandage is placed, and you can usually go home shortly afterward.
What should you expect after the injection?
Mild soreness or swelling at the injection site can occur for a day or two; icing and relative rest usually help. Avoid high-impact activity for 24–48 hours, but light walking is generally acceptable. Rarely, a transient “injection flare” with significant swelling can occur; your clinician can evaluate and drain fluid if needed.
How many injections and how often?
Protocols vary by product. Some regimens involve a single injection; others use a series (commonly weekly for 3–5 weeks). If effective, symptom relief may last several months, and repeat courses may be considered. Shared decision-making is important because efficacy varies across studies and individuals.
Risks and Benefits
How might knee gel injections help?
Hyaluronic acid (HA) adds viscosity and elasticity to the joint fluid, which can improve lubrication and shock absorption. Some people report less pain and easier movement, typically after a few weeks. Across studies, average pain relief is modest, and responses vary by individual.
How soon will I feel relief and how long can it last?
Time to effect often ranges from 2–6 weeks. When helpful, relief may last several months; some products are given as a single shot while others are a 3–5-week series. Repeat courses can be considered if prior benefit was meaningful.
What are the common side effects?
Most side effects are mild and short-lived: temporary soreness, swelling, warmth, or stiffness at the injection site. A small number of patients experience a transient injection flare with more pronounced swelling; clinicians can evaluate and, if needed, drain fluid to relieve symptoms. Serious complications (e.g., infection) are rare.
Are there any precautions or people who shouldn’t get HA injections?
HA products are FDA-cleared for knee OA pain in patients who have not achieved adequate relief with conservative care. They should not be injected into an infected knee or through infected skin, and they’re contraindicated in people with known hypersensitivity to product components. Some formulations are avian-derived. Your clinician will review allergies and local skin/knee conditions before treatment.
How do benefits compare with potential risks?
High-quality evidence shows HA provides small average pain reductions versus placebo and, in pooled data, a slightly higher rate of serious adverse events was observed, though the absolute risk remained low. Because of the small average benefit, some guidelines are cautious about routine use and emphasize shared decision-making.
Recovery: What to expect
Same day: Light activity is fine; expect mild soreness or swelling for 24–48 hours. Use ice and relative rest.
Activity limits: Avoid high-impact or prolonged standing until soreness settles; walking is typically okay.
Onset of relief: If effective, improvement usually appears in 2–6 weeks and may last several months depending on product and arthritis severity; single-shot and 3–5-week series exist.
Repeat courses: Consider another series only if a prior round gave meaningful benefit; timing varies by product label and payer policy.
When to contact a clinician
Seek prompt care if you develop any of the following after an injection:
Severe or rapidly increasing swelling or pain.
Fever or chills, warmth or redness over the knee.
Numbness, tingling, or trouble bearing weight.
Symptoms suggesting infection or an allergic reaction, especially if you have known sensitivities to avian proteins or product components.
Takeaway
Hyaluronic acid knee injections may ease pain and improve function for some people with knee osteoarthritis, usually beginning 2 to 6 weeks after treatment and lasting several months when effective. Average benefits across studies are modest, so shared decision-making is essential. If you try viscosupplementation, follow aftercare, watch for warning symptoms, and plan a reassessment to decide on repeat treatment or alternatives such as exercise therapy, weight management, medications, corticosteroid injections, PRP, or surgical consult when appropriate.
References
InformedHealth.org [Internet]. Cologne, Germany: Institute for Quality and Efficiency in Health Care (IQWiG); 2006-. Osteoarthritis of the knee: Learn More – Do knee injections help? [Updated 2024 May 15]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK544975/
Peck, J., Slovek, A., Miro, P., Vij, N., Traube, B., Lee, C., Berger, A. A., Kassem, H., Kaye, A. D., Sherman, W. F., & Abd-Elsayed, A. (2021). A Comprehensive Review of Viscosupplementation in Osteoarthritis of the Knee. Orthopedic reviews, 13(2), 25549. https://doi.org/10.52965/001c.25549
