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History of Arthrosamid®

Arthrosamid®’s story started two decades ago. The brainchild of the team at Contura, the product had been in human use for various indications since 2000, and a favourable safety profile had already been established.

Arthrosamid® — an OA treatment 20 years in the making

In April 2021, Arthrosamid®received CE mark (European market approval) for the symptomatic treatment of patients with knee osteoarthritis (OA), following the completion of a twelve-month prospective open-label study which saw participants experience significant pain reduction.1

The CE mark for Arthrosamid®represented a major milestone for a product that has been in development for more than 20 years — and fulfils an unmet clinical need for an effective, long-acting, safe and minimally invasive treatment that may postpone and potentially prevent knee surgery for those with OA.2 But what’s the backstory behind this novel, non-biodegradable hydrogel that is now expected to provide OA patients with life-changing pain relief and improved mobility? 1,3,4


Hydrogel is used in human indications


The story of Arthrosamid® began two decades ago when Contura’s patented hydrogel technology was initially used in humans. Contura had developed a number of hydrogel-based products and experience of its safe application was established with its use as an aesthetic bulking agent, which in turn led to its use as a bulking agent in women’s health treatments such stress urinary incontinence. The Contura team and its Chief Scientific Officer, Dr Ankorina Stark, aware of the physical properties of their unique hydrogel, were keen to investigate what happened when the product was injected into joints.



Rabbit study initiated and positive results are shown


Contura’s team of specialists commenced exploratory work on the joints of healthy rabbits in 2006. Initial doubts on its effect being limited due the hydrogel potentially being “ground” away within the joint, proved unfounded. Working with one of Denmark’s leading pathologist, Dr Lise Christensen, the team discovered that the product fully integrated into the synovial membrane of the joints with no adverse effects.5



Emile the cat receives treatment with hydrogel


With the positive data from the rabbit study on file, Dr Ankorina Stark had an opportunity to test out the hydrogel in another species when she was introduced to a friend’s cat. Overweight and with limited quality of life, Emile the cat was evidently experiencing severe joint pain and restricted mobility.

Teaming up with the vet with whom the team had worked on the rabbit study, Dr Ankorina Stark oversaw Emile’s treatment with the hydrogel in 2008. Within a few months and after one single injection, Emile was back on his feet and active again – and a happy patient.

Around the same time, Dr Ankorina Stark and her colleagues — led by Dr. Aziz Tnibar — instigated a further experimental model in goats, which demonstrated that the hydrogel appeared to be halting the development of OA and improving joint elasticity.6



First horse receives treatment - Lameness disappears and comes 4th in race


These results led the team to contact vets with samples of the hydrogel. Initially, they made little headway but this changed in 2009, when one of the vets, Linus Camitz, injected the hydrogel into a horse suffering severe lameness in two joints —experiencing such pain that its owner was considering having the animal put down. Within two weeks of a single injection of the hydrogel, the horse had experienced a 90% improvement in lameness and, weeks later, finished a race in fourth position – a result that had seemed impossible just a few months before.7 This opened the floodgates, with other owners keen to test drive this “life-saving” treatment on their horses.

At the same time, Contura had been considering opportunities for seeking a human indication for the product but the company was conscious it needed more evidence of the potential merits of the hydrogel in joints. With horses’ joints sharing a similar make up to those in humans, an equine study seemed the obvious way forward and would provide an opportunity to see the effects the hydrogel had on the synovial membrane in knees. The team subsequently embarked on a 24 month study in horses which provided them with the results they needed — after one single injection, more than 80% of the horses were lame free.7 Consequently, in 2009, Arthramid Vet was launched, providing a long-acting intra-articular injectable for the treatment of equine and canine lameness.



First human patient receives treatment with hydrogel


Behind the scenes, a pioneering consultant rheumatologist, Dr Andreas Hatkopp, had embarked on a series of small pilot investigations at his clinic in Denmark, using the product in several of his patients that were destined for knee replacement surgery. He had achieved encouraging results3,4 and, in 2010, he was introduced by a vet friend to one of the horse owners who was now experiencing significant joint pain himself. Having witnessed the positive benefits of the hydrogel first-hand, this individual was treated by Dr Hatkopp — and experienced an immediate improvement. Word of mouth soon saw Dr Hatkopp treating a number of patients compassionately off label, with positive results.3,4



Results reported after treatment of 80+ patients in observational proof-of-concept study


In parallel, Contura were continuing to undertake extensive biocompatibility and bench tests on the hydrogel and, in 2018, an observational proof-of-concept study of more than 80 patients treated with Arthrosamid® demonstrated the initial symptomatic pain relief was maintained for over a year.3



Contura commences multi-centre, randomised, controlled, double-blinded clinical study


This study was followed by a retrospective case series analysis which specifically addressed the safety aspects and the results confirmed that no safety signal of concern was raised.4 In 2019, Contura began a multi-centre, randomised, controlled, double-blinded clinical study of Arthrosamid® in patients with knee OA, enrolling more than two hundred people at four specialist treatment centres. This study sought to compare the reduction in pain achieved at various time points over one year following a single injection of Arthrosamid® with the reduction in pain achieved with a major brand of hyaluronic acid, a different injection treatment for the same indication. Again, the results for Arthrosamid® were positive, with the results of this study due to be published towards the end of 2021.8

Also in September 2019, Contura performed a study with the specific aim of seeking European approval. A prospective, open-label clinical investigation of Arthrosamid® in 49 patients with knee OA was performed at three specialist treatment centres in Denmark. This study measured the reduction in pain achieved at three months, six months, and 12 months, following a single injection of Arthrosamid®. Mirroring the results from the earlier observational proof-of-concept study, the data was positive — with Arthrosamid® treated patients experiencing a significant reduction in pain for over a year.1



In April, Un-restricted CE mark (European market approval) is granted for Arthrosamid® for the symptomatic treatment of patients with knee OA


And so, in April 2021, after 10 years of rigorous bench testing, biocompatibility testing, and clinical studies — and two decades after the idea to investigate the use of the product in joints was first suggested — Arthrosamid® was granted European approval for the symptomatic treatment of patients with knee OA.

Despite OA being the most common type of arthritis and the fastest-growing cause of disability worldwide9,10, the treatment area has seen little progression in the last 20 years. With so little known about exactly what causes knee OA, a permanent cure has yet to be discovered. Consequently, treatments have focused on managing the symptoms of the condition, meaning that the options available to those living with OA have been limited — until now.

Arthrosamid®is a new type of treatment that offers patients an effective alternative to current therapies. Providing sustained relief with one single injection, Arthrosamid®integrates into the synovial tissue to create a cushion-like effect that reduces pain and decreases stiffness. With the launch of Arthrosamid®, Contura aims to provide long-lasting pain relief to patients with knee OA — improving their quality of life and helping them to get moving again.

CE M Ark


1. 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.

2. Polyacrylamide hydrogel injection for knee osteoarthritis a 6 months prospective study (

3. Henriksen M et al. Intra-articular 2.5% polyacrylamide hydrogel for the treatment of knee osteoarthritis: an observational proof-of-concept cohort study. Clin Exp Rheumatol. 2018;36(6):1082-5.

4. Overgaard A et al Safety of Intra-Articular Polyacrylamide Hydrogel for the Treatment of Knee Osteoarthritis Symptoms: A Retrospective Case Series. Clin Ortho (2019) Adv Res J: COARJ-100001.

5. 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.

6. Tnibar A, Persson AB and Jensen HE. Mechanisms of Action of an Intraarticular 2.5% Polyacrylamide Hydrogel (Arthramid Vet) in a Goat Model of Osteoarthritis: Preliminary Observations. SM J Biomed Eng. 2017; 3(3): 1022

7. Tnibar, A., Schougaard, H., Koene, M., Christensen, L.H., Markussen, B., A controlled clinical trial on the efficacy of an intra-articular polyacrylamide hydrogel in horses with osteoarthritis. 23rd Annual Scientific Meeting of the European College of Veterinary Surgeons (ECVS), Copenhagen, July 2014.

8. A Multi-centre Randomized, Controlled, Double-blind Clinical Investigation of Intra-articular Polyacrylamide Hydrogel in Subjects With Knee Osteoarthritis Followed by an Open Label Extension Study.

9. Murray CJ, Vos T, Lozano R, et al. Disability-adjusted life years (DALYs) for 291 diseases and injuries in 21 regions, 1990–2010: a systematic analysis for the global burden of disease study 2010, Lancet, 2012, vol. 380 (pg. 2197-223).

10. Vos T, Flaxman AD, Naghavi M, et al. Years lived with disability (YLDs) for 1160 sequelae of 289 diseases and injuries 1990–2010: a systematic analysis for the global burden of disease study 2010, Lancet, 2012, vol. 380 (pg. 2163-96).