Introduction

Knee osteoarthritis is a common condition that affects millions of people worldwide, causing pain, stiffness, and reduced movement in the knee joint. These symptoms can make everyday activities challenging and significantly lower quality of life, especially for older adults. Finding effective ways to manage this condition is important, and among the many treatment options available, knee gel injections—often called hyaluronic acid or viscosupplementation injections—have become a popular choice for easing osteoarthritis pain.

In this article, we’ll explore how these injections work, look at the evidence supporting their benefits, and explain what patients can reasonably expect when considering this treatment.

What Is Viscosupplementation and How Does It Work?

Viscosupplementation is a treatment aimed at restoring the natural cushioning and lubrication inside the knee joint that is lost due to osteoarthritis. This is done by injecting a gel-like substance directly into the knee, which helps replace the joint fluid that normally keeps the bones moving smoothly.

The key ingredient in these injections is hyaluronic acid, a natural molecule found in healthy joint fluid. This fluid acts like a shock absorber and lubricant, allowing the knee to bend and straighten without pain or friction. In osteoarthritis, the amount and quality of hyaluronic acid decline, leading to stiffness and discomfort. The injection of extra hyaluronic acid replenishes this vital fluid, much like topping up oil in a car engine to reduce wear and tear. Beyond lubrication, this treatment may also protect joint cartilage and reduce mild inflammation, helping to ease symptoms further.

How Effective Are Hyaluronic Acid Knee Injections?

Research shows that hyaluronic acid injections can significantly reduce pain and improve knee movement for many people, particularly those with mild to moderate osteoarthritis. Most patients notice symptom relief within a few weeks, and the positive effects often last for several months — commonly up to six months, although this varies from person to person.

There are different brands on the market, such as Synvisc, Gel-One, and Hyalgan, which differ slightly in their formulation and source of hyaluronic acid. While this can influence how long the treatment lasts, all aim to restore joint lubrication and ease symptoms.

Compared with other treatments like nonsteroidal anti-inflammatory drugs (NSAIDs) or steroid injections, hyaluronic acid injections usually have fewer side effects, especially if used over the long term. Steroid injections often provide faster pain relief but are not suitable for frequent use. Understanding these differences helps patients and doctors choose the best treatment plan for each individual.

More recently, a newer option called polyacrylamide hydrogel (PAAG), known as Arthrosamid, has been studied alongside hyaluronic acid injections. One study found that “iPAAG offers comparable short-term efficacy and modest advantage at 6 months,” and that while pain returned to baseline for hyaluronic acid and steroid injections by 12 months, “iPAAG remained slightly improved.” This suggests that for some patients, PAAG injections might provide longer-lasting relief, although more research is needed to confirm these benefits.

What Happens During and After the Injection?

The process starts with a thorough consultation to make sure knee gel injections are right for the patient, considering their symptoms and joint condition.

During the appointment, the knee is cleaned, and the healthcare professional injects the gel directly into the joint using a fine needle. Most people feel only a brief pressure or mild discomfort during the injection, and local anaesthetic can be offered if needed.

After the treatment, patients are usually advised to rest the knee for a day or two and avoid heavy exercise to help the joint settle. Depending on the product and the individual’s condition, treatment might require a single injection or a series of up to five injections over weeks.

Improvement generally begins within days or weeks, with the best effects appearing around four to six weeks after treatment. Side effects are typically mild, such as temporary swelling or soreness, and usually clear up quickly. Patients should watch for any unusual or persistent symptoms and report them to their doctor.

Common Questions About Hyaluronic Acid Injections

Who can have these injections?
They are generally recommended for adults with mild to moderate knee osteoarthritis who haven’t found enough relief from conservative measures like exercise, weight loss, or oral painkillers. Those with very advanced joint damage or infections around the knee are usually not suitable candidates.

Are the injections safe?
Yes, they have a strong safety record with minimal risks when administered correctly. It’s important to discuss any allergies or existing infections with your healthcare provider before treatment.

How long do the effects last, and can I have repeat injections?
Most people experience relief lasting three to six months, but this can vary. Repeat treatments are possible and often done yearly or as your doctor advises.

What are the risks?
Side effects are usually minor and may involve temporary knee swelling or discomfort. Serious complications are very rare, especially when injections are done in a clinical setting by qualified professionals.

Conclusion

Hyaluronic acid knee gel injections provide a well-supported, patient-friendly option for managing osteoarthritis pain in the knee. By replenishing lost joint fluid, they help reduce pain and improve movement especially in early to moderate stages of the condition. While not a cure, these injections offer a safe and effective addition or alternative to other treatments, helping many people regain greater comfort and mobility.

Patients suffering from osteoarthritis of the knee should speak with their healthcare provider to see if this treatment is suitable for their individual needs.

References

Aykaç, B., Dinç, M., Nar, Ö. O., Karasu, R., & Bayrak, H. Ç. (2025). Comparative efficacy of polyacrylamide hydrogel versus hyaluronic acid and corticosteroids in knee osteoarthritis: A retrospective cohort study. Medicine, 104(38), e44655. https://doi.org/10.1097/md.0000000000044655