If you are considering Arthrosamid for knee osteoarthritis, one of the first questions may be how long the treatment lasts. The hydrogel itself is designed to remain permanently within the knee, while clinical studies have reported improvements in pain and function lasting for up to five years after one injection.

How Long Does Arthrosamid Stay in the Knee?

Arthrosamid injections use a non-absorbable hydrogel made from 97.5% water and 2.5% cross-linked polyacrylamide. Unlike treatments designed to break down or be absorbed over time, Arthrosamid integrates with the synovial tissue lining the joint.

According to the manufacturer's patient information, the hydrogel is intended to remain within the knee for its lifetime as an integrated part of the synovial tissue. It is described as non-biodegradable and non-absorbable rather than something that gradually disappears after several months.

Integration does not happen instantly. Manufacturer information indicates that the process is largely complete within approximately four to six weeks following the injection.

However, the fact that the hydrogel remains in the joint should not be confused with a guarantee that pain relief will remain unchanged permanently.

How Long Can the Benefits Last?

Current published evidence has followed patients for as long as five years after treatment.

A 2026 follow-up study assessed people with moderate-to-severe knee osteoarthritis who had received a single injection of 2.5% polyacrylamide hydrogel. Of the 119 people originally treated, 91 entered the long-term extension and 58 completed five years of follow-up. Improvements in pain, stiffness and physical function remained evident at five years among those assessed.

Earlier research has also reported improvements over shorter periods. A 2025 prospective cohort study involving 314 treated knees found improvements in osteoarthritis symptoms during 24 months of follow-up, although the study had no control group and outcomes differed according to factors such as osteoarthritis severity.

These results mean that Arthrosamid injections may provide prolonged symptom relief for some patients. They do not mean that every person will experience the same degree or duration of benefit.

Your response can depend on factors including the severity of your osteoarthritis, your general health, your activity levels and the condition of the knee before treatment.

Does One Injection Last Forever?

It is helpful to separate the physical presence of Arthrosamid from its clinical effects.

The hydrogel is designed as a permanent implant and remains integrated within the knee. However, osteoarthritis is a long-term condition that can continue to change over time. A permanent hydrogel therefore does not mean that knee osteoarthritis has been permanently cured or that you will never experience pain again.

Research to date provides encouraging evidence of sustained symptom improvement, but the evidence base is still developing. NICE considered Arthrosamid for Health Technology Evaluation guidance but did not select it because the panel concluded that there was insufficient evidence for that guidance process.

This is why treatment should be discussed in terms of realistic goals, such as reducing pain, improving function and helping you carry out everyday activities more comfortably, rather than promising a specific number of pain-free years.

What Happens If Knee Pain Returns?

If your symptoms start to increase after Arthrosamid injections, you should have your knee reassessed rather than assuming that you automatically need another injection.

Your clinician can consider whether the change relates to osteoarthritis progression, another knee problem or a change in your overall health and activity. They can then discuss the most appropriate next step based on your current symptoms.

Treatment for knee osteoarthritis may also include therapeutic exercise, weight management where appropriate, medicines and other interventions. Your treatment plan should consider your overall condition rather than relying on one treatment alone.

Find Out Whether Arthrosamid Is Right for You

Arthrosamid is designed to remain permanently within the knee, while published clinical research has reported improvements in pain and physical function for up to five years following a single injection. Individual results can vary, and five-year evidence should not be interpreted as a guaranteed duration of pain relief.

If knee osteoarthritis is affecting your mobility or quality of life, contact Regenesis for a specialist assessment and discuss whether Arthrosamid injections may be suitable for your symptoms and treatment goals.