Hydrogel injections are being explored as a non-surgical option for managing joint pain, particularly knee osteoarthritis. But how long can the effects last? Current research suggests that certain polyacrylamide hydrogel injections may provide sustained symptom improvement for several years, although individual results can vary considerably.

How Long Can Hydrogel Injections Provide Relief?

The answer depends on the type of hydrogel being used. For 2.5% polyacrylamide hydrogel, which has been studied as an intra-articular treatment for knee osteoarthritis, published research has reported improvements in pain and function lasting for up to five years after a single injection.

A 2026 study following patients with moderate-to-severe knee osteoarthritis found that improvements in pain and physical function remained evident five years after treatment. Another five-year study also reported sustained improvements following a single injection, although not everyone who originally entered the studies completed the full follow-up period.

That does not mean every patient who receives hydrogel injections will experience five years of pain relief. Treatment response varies, and factors such as the severity of osteoarthritis, overall joint health, activity levels and individual response may influence the outcome.

It is also important not to apply these results to every type of hydrogel or every painful joint. Much of the available long-term clinical evidence currently relates specifically to polyacrylamide hydrogel used for knee osteoarthritis.

How Do Hydrogel Injections Work?

Polyacrylamide hydrogel is injected directly into the affected knee joint. Unlike a tablet that circulates throughout the body, an intra-articular treatment is delivered to the joint itself.

The intention is to provide a longer-lasting treatment option for people with osteoarthritis-related symptoms. Clinical studies commonly assess changes in pain, stiffness and physical function to determine whether patients experience meaningful improvement after treatment.

However, hydrogel treatment does not mean that osteoarthritis has been cured. Osteoarthritis is a long-term condition involving changes within the joint, and treatment generally focuses on reducing symptoms and maintaining function.

Regenesis therefore considers treatment as part of a wider assessment of the patient, their symptoms and their individual goals rather than viewing any injection as a guaranteed solution.

Are Hydrogel Injections Suitable for Everyone?

Not necessarily. A clinician should first establish what is causing your joint pain and whether an injectable treatment is appropriate.

This distinction matters because joint pain can have many causes. Even where osteoarthritis is present, treatment decisions may depend on which joint is affected, symptom severity, previous treatments, general health and how much the condition interferes with everyday activities.

The evidence surrounding newer hydrogel treatments is also still developing. NICE considered Arthrosamid, a polyacrylamide hydrogel treatment for symptomatic knee osteoarthritis, for potential guidance development but did not select it for Health Technology Evaluation guidance because the panel considered the available evidence insufficient at that stage.

This does not mean that published studies have shown no benefit. Rather, it highlights why patients should receive balanced information about both the available research and its limitations before deciding whether hydrogel injections are right for them.

What Happens When the Benefits Begin to Reduce?

There is no exact date when the effect of treatment will suddenly stop. Some patients may experience improvement for a prolonged period, while others may notice less benefit or respond differently from the outset.

Osteoarthritis can also progress over time. This means changes in pain years after an injection may reflect both the treatment response and changes occurring within the joint itself.

Your clinician can review your symptoms if pain begins to return. Depending on your circumstances, this may involve reassessing your diagnosis, reviewing activity and rehabilitation, discussing other non-surgical treatments or considering whether further intervention is appropriate.

Treatment decisions should always be based on your current symptoms and clinical assessment rather than assuming that a previous injection simply needs to be repeated.

Explore Your Options for Joint Pain

Current studies of 2.5% polyacrylamide hydrogel for knee osteoarthritis have reported sustained improvements for up to five years after a single injection, but this should not be interpreted as a guaranteed five-year result for every patient.

If joint pain is affecting your mobility or quality of life, a specialist assessment can help identify the cause and determine which treatment options may be suitable. Contact Regenesis to discuss your symptoms and learn more about the non-surgical orthopaedic treatments available.