Evidence

The research behind Arthrosamid.

Understanding the evidence for polyacrylamide hydrogel injections in knee osteoarthritis, and what published outcomes mean for your decision.

269

Patients

314

Knees Treated

Months Follow-up

Featured 2025 Study

Polyacrylamide hydrogel injections in knee osteoarthritis: a PROMs-based 24 month cohort study

Journal of Clinical Orthopaedics and Trauma, 2025. Co-authored by Professor Paul YF Lee.

Read primary study

Study paper cover from Journal of Clinical Orthopaedics and Trauma

What changed for the people in the study

The published cohort reported improvements in pain and knee function over the two-year follow-up period. The study tracked progress using three standard clinical measures.

How much does your knee hurt?

Pain intensity

Visual Analogue Score

Pain levels

A standardised scale used clinically to measure the severity of knee pain experienced by patients during their daily activities.

How easily can you manage daily activities?

Ease of everyday movement

Oxford Knee Score

Everyday function

A focused questionnaire assessing how well patients can manage practical physical tasks like walking, navigating stairs and shopping.

Which symptoms affect your movement?

The symptoms you experience

Lysholm Knee Score

Specific symptoms

Detailed evaluation of specific mechanical symptoms including limping, catching, swelling, and stability of the joint during movement.

Study Overview

The peer-reviewed cohort recorded improvements in pain, Oxford Knee Score and Lysholm knee-function measures through 24 months in routine specialist care.

The results provide practical evidence for treatment discussions and show why stage of osteoarthritis and health factors such as diabetes matter when selecting patients.

269 Patients

Total participants enrolled

314 Knees

Treated with specialist care

Follow-up up to 24 months

London and Lincolnshire centers

Prospective clinical study design

Single-injection Arthrosamid® treatment

Bilateral Treatment: Some patients received injections in both knees where clinically appropriate.

How to interpret the evidence

The numbers below come from the peer-reviewed London Cartilage Clinic/MSK Doctors paper. They are published study findings, not clinic activity totals. The design, safety observations and knee-replacement outcomes should be read alongside the improvements reported for the group.

Arthrosamid 24-month observational cohort design and outcomes

Item	Published report	How to interpret it
Design and population	Prospective observational cohort; 269 patients, 314 knees	Real-world cohort, not a randomised trial
Follow-up	Up to 24 months	An observed study period, not a duration guarantee
Pain (VAS)	Mean 6.64 at baseline; 5.06 at 24 months	Group mean; individual responses varied
Oxford Knee Score	Mean 25.35 at baseline; 31.95 at 24 months	Observational design without a control group
Lysholm score	Mean 45.22 at baseline; 56.15 at 24 months	No untreated or active comparator group
Complications and tolerance	Across 314 treated knees: pain 51 (16.2%), effusion 52 (16.6%), swelling 47 (15.0%), overlying skin infection 3 (1.0%), deep infection requiring washout 2 (0.6%).	Reported during follow-up in this cohort; these are not an individual risk prediction or a separate clinic safety audit.
Knee replacement	49 of 244 treated knees in the study’s age-50-and-over replacement analysis required replacement within two years.	More advanced arthritis was associated with progression. This does not establish that the injection prevents or delays surgery.

Primary peer-reviewed paper

Read the full peer-reviewed cohort or use the DOI record. The publication describes the prospective cohort design, patient population, outcome measures, subgroup findings, complications and progression to knee replacement.

Professor Lee also co-authored a 2022 systematic review of five early reports covering 463 combined patient outcomes and a separate single-patient patellofemoral case report. Those designs are supporting context, not equivalent to the larger prospective cohort; individual results vary.

Evidence is not the same as reviews

A patient review describes one person's experience and can help assess service, communication and aftercare. It cannot establish treatment efficacy, incidence of complications or the result another patient should expect.

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How the study measured change

Patients completed established measures of pain (VAS), everyday function (Oxford Knee Score) and knee performance (Lysholm score) before treatment, at six weeks, six months, one year and two years.

The researchers also recorded age, medical conditions including diabetes, arthritis severity, whether one or both knees were treated, complications and progression to knee replacement. Clinically important change thresholds helped distinguish meaningful improvement from small score changes.

Who improved—and where caution matters

Average scores improved, but responses varied. Exploratory analysis associated older age, a lower arthritis grade, absence of diabetes and bilateral knee involvement with a greater chance of reaching meaningful improvement across all three measures. These associations are not a validated prediction tool.

Patients with more advanced arthritis were more likely to progress to knee replacement. An injection acting on the joint lining cannot replace lost joint surfaces. For substantial pain, deformity or loss of function, a surgical opinion may be the more useful next step.

Compare Arthrosamid and knee replacement →

Active lifestyle goal representing knee recovery

What this means for your knee

These findings help inform a conversation about your knee: what you would like to do more easily, what your scans show and which options fit your goals.

Questions to explore in your assessment:

How do your symptoms match those measured in the study?
What do your personal scans suggest about suitability?
Which practical everyday activities are your primary goal?

About this study's design

Prospective observational cohort: This study followed a specific group of treated patients over time in a real-world clinical setting. It is not a randomised controlled trial comparing Arthrosamid against a placebo.

Follow-up duration: The 24-month period refers to the length of time these patients were actively tracked by researchers. It is a measurement milestone, not a guaranteed duration of benefit for future patients.

From research to your treatment decision

We use the evidence alongside your diagnosis, scans, previous care and goals. Arthrosamid is not a routine recommendation for every painful knee: we discuss expected benefit, risks and alternatives, and decline treatment when it is unsuitable.

The two-year follow-up is a study milestone, not a promise of two years of relief. Arthrosamid does not cure arthritis, regenerate cartilage or establish that surgery can be delayed. A questionnaire can organise your concerns, but suitability is a clinical decision.

Start your suitability assessment or read how we assess your knee.

Supporting research library

Additional published reviews and case reports.

Systematic Review 2022 • Medical Research Archives

Early reports of polyacrylamide hydrogel outcomes

A structured review combining clinical data from five early reports detailing 463 patient outcomes following treatment.

View source

Single Case Report 2022

Patellofemoral bone marrow lesions

A documented single-patient case report detailing the specific clinical presentation and outcome for an individual with this lesion type.

View details

Professor Paul Lee, Consultant Orthopaedic Surgeon

Clinical context in practice

Professor Paul YF Lee, Consultant Orthopaedic Surgeon

Research provides the foundation, but it is just one part of your decision. In clinic, we discuss these published findings alongside a physical examination, your specific imaging, and the activities you want to get back to. This determines if Arthrosamid is a practical option for your knee.

Book a free discovery call Consultation booking

Common questions about the research

What exactly did the cohort study measure?

The study measured patient-reported outcomes using three standard clinical tools: the Visual Analogue Score (for pain), the Oxford Knee Score (for everyday function), and the Lysholm Knee Score (for specific symptoms). It tracked these scores in 269 patients over a 24-month period following their injection.

Does "24 months" mean the treatment stops working after two years?

No. The 24 months represents the duration that researchers actively followed up with this specific group of patients. It is a measurement timeframe, not a guaranteed expiry date for relief. Individual outcomes and duration of benefit vary based on the specific condition of your knee.

How should I use these findings when speaking to a doctor?

Use these findings to ask targeted questions during your assessment. You might ask how your current symptoms compare to those measured in the study, or whether your scan results suggest you are a suitable candidate based on the clinic's broader experience with this treatment.

Does Arthrosamid® really work for knee osteoarthritis?

Published evidence shows group-level improvements in pain and knee function through 24 months. A prospective observational cohort of 269 patients and 314 knees reported group-level improvements through 24 months. Results vary between individuals, so diagnosis, imaging and suitability assessment remain important.

How long do Arthrosamid® results last?

The published cohort followed group outcomes for 24 months. That is the study period, not a guaranteed duration of benefit. Improvement may develop over the following weeks, with the clinic's early review at around six weeks. Individual onset, size and duration of response vary.

Can the evidence predict who will respond to Arthrosamid®?

The cohort found better outcomes were associated with factors including lower-grade knee osteoarthritis and the absence of diabetes. These group associations inform patient selection but do not predict an individual response. Diagnosis, imaging, contraindications, function and alternatives still require clinical assessment. See the Arthrosamid® suitability self-assessment for a structured indication of fit.

What happens if Arthrosamid® does not work for me?

If improvement is absent or below expectations, the clinic reviews the diagnosis, imaging, function and other pain sources rather than assuming another injection is the answer. Rehabilitation, another non-surgical option or a surgical opinion may be more appropriate.

Is the Arthrosamid® evidence peer-reviewed?

Yes. The London Cartilage Clinic/MSK Doctors 24-month prospective cohort is peer reviewed and linked on this page by full text and DOI.

Will Arthrosamid® prevent me from needing a knee replacement?

Arthrosamid® is not a substitute for knee replacement where replacement is clinically appropriate. Arthrosamid has not been proved to delay or prevent knee replacement. It may be considered for symptom management in an appropriately selected adult, while advanced disease, deformity or major functional loss may make replacement assessment more suitable.