25th October 2021

New hydrogel injection for knee osteoarthritis offers patients a return to mobility without surgery

Safe and sustained pain relief with a single injection.

A new hydrogel injection for knee osteoarthritis that harnesses non-biodegradable hydrogel technology – Arthrosamid® – was officially launched to the UK market at the British Orthopaedic Association (BOA) Annual Congress, 21st- 24th September 2021.

New hydrogel injection for knee osteoarthritis

Pioneered by Contura International Ltd, , Arthrosamid® offers an alternative to current therapies and fulfils an unmet clinical need for an effective, long acting, safe and minimally invasive treatment to alleviate pain associated with knee osteoarthritis (OA).

The treatment has the potential to change the present care pathway for managing OA, which affects approximately 8.5 million people in the UK1. Around 1 in every 5 people aged over 45 in England is affected by knee osteoarthritis2 and current treatments are not long lasting or involve invasive knee replacement surgery. Despite a large suffering population, there has been very little innovation in the range of OA treatments on offer to meaningfully help patients – until now.

Consisting of 2.5% cross-linked polyacrylamide and 97.5% non-pyrogenic water, a 6ml dose of Arthrosamid® is injected into the joint space to cushion the knee and relieve pain in one single treatment3. Patients can expect to see improved mobility and pain relief within days where the effect is long lasting4.

A number of clinical studies have been completed into Arthrosamid® with further trials ongoing:

  • A prospective open label study5, “IDA”, demonstrated Arthrosamid®’s effect in reducing pain at 6 months, which was maintained at 12 months. This trial, together with the safety and performance data established for the hydrogel technology, satisfied European regulatory authorities to grant approval (CE Mark) to Arthrosamid® for the symptomatic treatment of patients with knee OA. Data published in Osteoarthritis and Cartilage in 2021 found that over 70% of patients had a positive experience of treatment, exceeding a minimal clinically important difference, with a reduction in pain, stiffness and physical mobility at 6 months with pain and physical function maintained beyond one year.6
  • Positive results from a separate multi-centred, randomised, controlled 1-year clinical study, “ROSA”, of Arthrosamid® in 238 patients with knee OA are expected to be published towards the end of 20217. The study seeks to compare the reduction in pain after one year following a single injection of Arthrosamid® with the reduction in pain achieved with a major brand of hyaluronic acid, a common treatment for the same indication. The study will follow patients out to 5 years.

Arthrosamid® injections are now being introduced to patients through a network of leading orthopaedic clinicians across the UK including Professor Martyn Snow at the Birmingham Knee and Shoulder Clinic, Professor Paul Lee at 108 Harley Street and Mr Sanj Anand, The OrthTeamcentre, Manchester.

Mode of Action

Once injected into the intra-articular cavity, Arthrosamid® integrates into the synovial tissue of the inner joint capsule and thickens the synovial membrane. The non-absorbable, non-biodegradable and non-migratory characteristics of Arthrosamid® provide durable cushioning of the inner capsular tissue, thereby reducing pain, decreasing joint stiffness, and improving the function of the knee affected by OA8. Unlike other types of intra-articular injections, such as hyalurons, which solely function as visco-supplements, Arthrosamid® is physically different as it becomes an integrated part of the soft synovial tissue in the joint capsule9 and is therefore expected to exert its effect for a substantially longer time than older generation OA treatment such as cross-linked hyalurons.

New hydrogel for knee osteoarthritis

The treatment has been 20 years in the making, having an interesting heritage as a veterinary product and as a treatment used in humans for various conditions. A detailed understanding of hydrogel’s biocompatibility has been derived from pre-clinical and histological studies in goats and rabbits.

In addition, over the last 10 years, extensive experience in equine medicine has been gained with several thousand horses with OA having been treated with the hydrogel technology, Arthramid Vet® – the trade name for veterinary use. In that time, significant improvements initially at 12 months and lasting to 24 months were demonstrated with studies showing that after one injection, 80% of the horses were lame-free.10

The journey to realise the product’s potential to treat joint pain in humans was led by pioneering consultant rheumatologist Dr Andreas Hartkopp who, in 2010, embarked on a series of small pilot investigations at his clinic in Denmark11, using the product in several of his patients that were destined for knee replacement surgery. The results were encouraging and over time, Dr Hartkopp began treating a number of patients for compassionate use, with positive results.

Over recent years, studies in hundreds of patients across different sites have confirmed the consistency of effect with Arthrosamid® and further studies involving experts from across Denmark are underway to support its role in treating patients with knee OA. Mr. Sean Curry, Consultant Orthopaedic and Trauma Surgeon at The London Orthopaedic Clinic at King Edward VII, London who presented at a thought-leadership session on Arthrosamid® at BOA Congress explains:

Rakesh Tailor, Chief Operating Officer at Contura International Ltd comments:

“After 10 years of rigorous testing, biocompatibility analyses and clinical studies, and two decades after the idea to investigate the use of hydrogel in human joints was first suggested, we’re delighted that Arthrosamid® is now available as a treatment for pain associated with knee OA. The discomfort caused by OA can significantly impact a patient’s quality of life and make everyday activities challenging. For patients under 70 who are deemed too young for knee replacement surgery, Arthrosamid® particularly represents a game changing option where a single treatment injection provides long lasting pain relief and mobility without the need for surgery. We are excited to work with experts to establish what is potentially a new treatment algorithm for patients suffering with knee OA.”

Contact the Contura Orthopaedic Team for an appointment.


1. National Institute for Health and Clinical Excellence - Centre for Clinical Practice Osteoarthritis Final Scope

2. Arthritis UK: Prevalence of osteoarthritis in England and local authorities: Birmingham

3. Christensen, L., Camitz, L., Illigen, K.E., Hansen, M., Sarvaa, R., Conaghan, P.G., 2016. Synovial incorporation of polyacrylamide hydrogel after injection into normal and osteoarthritic animal joints. Osteoarthritis and cartilage / OARS, Osteoarthritis Research Society 24, 1999-2002.

4. OARSI CONNECT 2021 POSTER 336 POLYACRYLAMIDE HYDROGEL INJECTION FOR KNEE OSTEOARTHRITIS: RESULTS OF A 52 WEEK PROSPECTIVE STUDY Henning Bliddal, Anders Overgaard, Andreas Hartkopp, Jannie Beier, Philip G Conaghan, Marius Henriksen.

5. Bliddal H, Overgaard A, Hartkopp A, Beier J, Conaghan PG, et al. (2021) Polyacrylamide Hydrogel Injection for Knee Osteoarthritis: A 6 MonthsProspective Study. J Orthop Res Ther 1188:6.

6. Bliddal H, Overgaard A, Hartkopp A, Beier J, Conaghan PG, et al. (2021) Polyacrylamide Hydrogel Injection for Knee Osteoarthritis: Results of a 52 Week Prospective Study. Osteoarthritis and CartilageVol. 29 S278: 2021.

7. Treatment of Knee Osteoarthritis With PAAG-OA - ClinicalTrials.gov

8. Christensen, L., Camitz, L., Illigen, K.E., Hansen, M., Sarvaa, R., Conaghan, P.G., 2016. Synovial incorporation of polyacrylamide hydrogel after injection into normal and osteoarthritic animal joints. Osteoarthritis and cartilage / OARS, Osteoarthritis Research Society 24, 1999-2002.

9. Christensen, L., Daugaard, S., 2016. Histological Appearance of the Synovial Membrane after Treatment of Knee Osteoarthritis with Polyacrylamide Gel Injections: A Case Report. Journal of Arthritis 5, 217.

10. Tnibar, A., Schougaard, H., Camitz, L., Rasmussen, J., Koene, M., Jahn, W., Markussen, B., 2015. An international multi-centre prospective study on the efficacy of an intraarticular polyacrylamide hydrogel in horses with osteoarthritis: a 24 months follow-up. Acta veterinaria Scandinavica 57, 20.

11. Henriksen, M., Overgaard, A., Hartkopp, A., Bliddal, H., 2018. Intra-articular 2.5% polyacrylamide hydrogel for the treatment of knee osteoarthritis: an observational proof-of-concept cohort study. Clinical and experimental rheumatology 36, 1082-1085.