Osteoarthritis is the most common form of arthritis affecting the knee joint. It is becoming more common in younger people. Treatment options include exercise, weight loss, medication, injections, and knee joint replacement. A new type of injection called an Arthrosamid gel shows more promise than other injections in reducing the pain of knee arthritis. So, what is Arthrosamid UK, and how effective is it in knee arthritis?
Osteoarthritis
Osteoarthritis is a chronic condition commonly affecting the knee joint. It wears away the shock-absorbing cartilage of the joint’s surface, causing bone-on-bone rubbing. This bone contact leads to inflammation, stiffness, and joint pain. Pain from knee arthritis comes from inflammation produced by the joint rather than cartilage wear.
Treatment options for osteoarthritis
The most effective treatments for knee osteoarthritis include exercise therapy and weight loss. Medications such as ibuprofen can also help. In addition, we use injections into the knee joint for more severe cases of knee arthritis. Common injections for knee arthritis include cortisone, hyaluronic acid, and PRP. Recently, a new type of injection called Arthrosamid offers people an effective alternative to currently available injection therapies.
What is Arthrosamid UK?
Arthrosamid UK is a new hydrogel material with water molecules (97%) attached to a polyacrylamide backbone (2.5%). It is non-degradable, meaning the body can’t break it down. Moreover, it is unlike acrylamide, which is shown to be toxic in humans.
Doctors have used hydrogel as a bulking agent for medical problems, such as stress incontinence and face filler, for over 20 years. In joints, it has been used extensively in horses with arthritis since 2009 and in humans in 2010. Biological studies have shown that Arthrosamid is inert and doesn’t react with different tissues, including muscle, bone and joints.
Over 15000 Arthrosmaid injections have been performed in Europe and the UK since the approval for use in 2020.
How does Arthrosamid UK work?
The synovium is a thin membrane lining the joint and contains synovial cells. These cells produce joint fluid to lubricate and keep the joint healthy.
When we inject hydrogel into the knee joint, it is taken up by the synovial cells and forms a new joint lining. This new lining reduces knee joint inflammation, leading to less pain. The gel also produces cushioning and lubrication. Forming a new joint lining can take up to four weeks.
A New Laboratory study supports Arthrosamid gel mechanism of action theory
A new study examined how Arthrosamid works in knee arthritis. Scientists performed biopsies of the knee after an Arthrosamid injection. They found that the gel was taken up by the cells lining the joint, also called the synovial cells. These cells made a new ‘pseudo’ joint lining or barrier.
Evidence in Knee Osteoarthritis
First, two promising studies published about ten years ago showed that hydrogel injected in arthritis knees showed excellent results starting at four weeks and continuing until 26 weeks. Follow-up studies showed this effect persisted for years.
A further randomised controlled trial between Arthrosamid and hyaluronic acid in people with knee arthritis showed similar improvements at one year. However, in younger (70 years) and slimmer patients and patients with a large effusion, Arthosamid performed better than hyaluronic acid. In this study, Arthrosamid had an overall 73% positive response rate to Arthrosamid gel in this RCT. But this response is dependent on age, with younger patients doing much better:
- <60 years: 94%
- <70%: 80%
- Over 70s: 63%
The pain-relieving effect starts at four weeks and is maximal at about 12 weeks. However, one recent study from Turkey indicates that the pain-free effect may take up to six months to reach the maximum impact. Sometimes, pain-relieving effects can begin within two weeks.
Also, the average improvement in pain and function is 20-25%, starting at twelve weeks. Moreover, this positive effect lasts longer than other injectables. Recently released longer-term data from RCT suggests that the positive effect lasts at least five years and perhaps beyond. For comparison, hyaluronic acid and PRP last about a year.
A new study suggests that Arthrosamid works better than hyaluronic acid in a swollen knee.
An RCT study comparing Arthrosamid to Synvisc-1 (hyaluronic acid) found that patients with swelling in the knee joint responded better to Arthrosamid at six months. So, if you have a swollen knee, consider Arthrosamid rather than Synvisc-1 to relieve pain and improve function in knee arthritis.
How do we deliver Arthrosamid injection?
We inject this hydrogel directly into the knee joint. We strongly suggest that you have this procedure with ultrasound guidance. The hydrogel must be delivered accurately in the joint rather than outside it. Without ultrasound guidance, the accuracy of a knee injection is at most 50-80 %. Therefore, one in three to five injections without guidance does not get into the joint.
Generally, your doctor will give you a local anaesthetic on the skin. Then, your doctor will insert a needle with ultrasound guidance into the knee joint. If your knee has a large amount of swelling, your doctor may drain the knee first. The hydrogel is injected directly into the joint through the needle. Your doctor must inject it with a sterile technique. Please look at the video below of Dr Masci using ultrasound guidance to inject it into a person’s knee joint.
What should you expect immediately after the procedure?
Following the procedure, we will observe you for 15 minutes. You might feel a tightness or mild pain once the local anaesthetic wears off. So, it would be best to continue with your regular medications and painkillers.
Receiving Arthrosamid may feel like a different sensation from other treatments that you have previously experienced, as it is denser than other injectables.
Injection side effects
Generally, this implant is well-tolerated.
The most common side effect is pain and discomfort at the injection site. The knee joint may also feel full or distended, and swelling of the Baker’s cyst may occur. This effect is usually mild, can last from 2 days to 4 weeks, and occurs in 10-20% of patients. We treat a flare with reduced activity, regular ice packs and oral anti-inflammatories such as ibuprofen.
Rare side effects include allergic reactions and infection. However, the rate of serious adverse effects is very low. Three suspected cases of infection have been reported in over 15000 Arthrosamid injections. (0.02%).
How does Arthrosamid UK differ from other injections?
Arthrosamid differs from other injects, such as hyaluronic acid, PRP, or stem cells. The hydrogel is non-absorbable, which lasts longer in the joint, providing lubrication. Conversely, the body quickly degrades hyaluronic acid and PRP, so the effect is limited and less potent.
Arthrosamid injection UK cost
Dr Masci performs this injection for £2400. He performs this procedure with ultrasound guidance to improve accuracy. He has over fifteen years of experience in ultrasound-guided procedures and teaches doctors and physiotherapists how to inject with ultrasound.
Other frequently asked questions:
When can you return to sport about an Arthrosamid gel injection?
Generally, we suggest you rest your knee from exercise for about 10 days after the hydrogel injection. Short-term rest reduces the chances of a flare or swelling. The onset of the pain-relieving effect is four weeks, although it may take longer.
An example of a return to running after an injection:
On Day 1 post-injection: complete rest, ice and oral ibuprofen for pain
Day 2 post-injection: Restart upper body weights, swim without kicking and continue ice and ibuprofen for a flare.
On Day 3-5 post-injection: Continue upper body weight, swimming with kicking, light cycling
Day 6-7 post-injection: Continue upper body weights, swimming, light cycling, and start lower body weights at 50% of the usual intensity.
Day 10 post-injection: Start running depending on pain.
Is an Arthrosamid gel a type of hyaluronic acid?
No. Hyaluronic acid is found in tendons, ligaments, and joints, so the body quickly breaks it down. On the other hand, Arthrosamid hydrogel is non-degradable, meaning it lasts longer in the knee joint.
Are there any contraindications to using Arthrosamid gel?
Generally, we should not inject Arthrosamid if:
- If the knee has active skin or joint infection
- You have been injected with cortisone, hyaluronic acid, or PRP. It would be best to wait until the body has absorbed the cortisone or hyaluronic acid (the exact time varies depending on the drug).
- The knee contains metal for a replacement
- You have had a knee arthroscopy within six months
- You have infections in other joints
- You have an inflammatory arthritis, such as psoriatic arthritis.
- Minors (less than 18 years) or pregnant women
Are there any studies comparing Arthrosamid gel to PRP?
No. However, one study compared hydrogel to Synvisc-1, a type of hyaluronic acid. In this study, both Arthrosamid and Synvic-1 performed equally at 12 months. However, the data at four years shows that the positive effect of Arthrosamid continues.
I’ve just had a Durolane injection into my knee. Do I have to wait before having an Arthrosamid injection?
Yes, the guidelines suggest waiting until the body has broken down the Durolane before administering Arthrosamid. We suggest waiting three months to allow complete breakdown of the Durolane.
Can you have Arthrosamid gel injected without imaging?
Yes, but we don’t recommend it. We know that using ultrasound improves the accuracy of a knee joint injection. For example, studies suggest knee injections without ultrasound are only 60-80% accurate compared to ultrasound, with 100% accuracy. So, if you’re thinking about Arthrosamid, you should ensure you have it injected with ultrasound.
Why are prophylactic antibiotics recommended?
As Arthrosamid is non-degradable, you must have antibiotics. A high concentration of an antibiotic at the time of the injection reduces infections. So far, there have been three suspected infections in over 140000 infections.
How long does Arthrosamid UK take to work?
According to company data, pain relief usually starts at four weeks. The maximal effect is generally at 3 months but may take longer. In one recent study from Turkey, positive effects may take up to six months to reach the maximum impact.
How much does Arthrosamid reduce pain and improve knee function?
Arthrosamid improves pain and function by 20-25% on average. This effect starts at six to twelve weeks, with a maximal effect at 4-6 months.
How long does Arthrosamid last?
Studies suggest Arthorosamid lasts for more than a year. A recent study published in 2025 shows that Arthrosamid lasts for at least five years. In this data, younger patients under 70 had a better effect than older patients. This effect compares favourably to other injectables, such as hyaluronic acid and PRP, which last about a year.
The makers of Arthrosamid have committed to obtaining more data to learn who responds best to Arthrosamid.
Can Arthrosamid be used for arthritis in other joints?
Some practitioners have used Arthrosamid for hip, ankle, and shoulder arthritis. However, this drug has not been approved for use in other joints, so we do not recommend it.
Can we use Arthrosamid for inflammatory arthritis such as psoriatic or rheumatoid arthritis?
While Arthrosamid may work well in inflammatory arthritis, it has not been approved and should not be used.
When will Arthrosamid UK be available in the USA?
Contura has applied for FDA approval and is well into the process of getting Arthrosamid approved in the States. They have also applied to regulatory bodies in Canada and Australia. It is hard to predict when the approval process will be completed.
Is Arthrosamid UK available on the NHS?
No. However, we are conducting studies at various NHS trusts throughout the UK. You can contact your local trust to find out more.
Can you have a knee replacement after an Arthrosamid injection?
Yes. Unlike other injectables, such as cortisone, there have been no concerns about having surgery after Arthrosamid.
About 10% of patients who had an Athrosamid injection went on to have a total knee replacement.
Safety data has extended to about 15 years, with 90 knees having a knee replacement after Arthrosamid. This cohort has had no reports of problems during or after the knee replacement.
Do higher-risk patients, such as diabetes or obese patients, have a different response?
Perhaps. The effectiveness of Arthrosamid drops by about 10% compared to nondiabetic patients. However, having diabetes is not a contraindication. For obese patients, the effect of Arthrosamid is similar to that of non-obese patients. Losing weight will also help with pain reduction.
Can people with a history of active cancer have Arthrosamid gel?
Yes. Arthrosamid is not a contraindication with active cancer patients, unlike other injectables such as PRP.
We know that some patients don’t respond to Arthrosamid gel. Can some patients get worse after Arthrosamid?
Yes. While the majority of patients improve with Arthrosamid, some don’t, and some can get worse. Recent data shows that about 5-20% of patients can have worse scores after an Arthrosamid injection. This data is not unlike other injects such as hyaluronic acid, PRP or stem cells. Worsening scores may be due to deteriorating arthritis rather than the Arthrosamid.
Can I receive treatment in both my knees?
Yes. However, as a general rule, we suggest separating the injections by at least a week and not having them done at the one consultation.
If I have a partial positive effect from Arthrosamid, can I have a top-up injection?
Yes, but we suggest you wait about 6 months before having a top-up injection, as Arthrosamid can take up to 6 months for its full effect. Top-up injections are usually 3mls compared to 6mls for the initial injection.
Final word from Sportdoctorlondon about Arthrosamid UK
Could Arthosamid be a game changer for people with intractable knee arthritis? Potentially yes. We suggest considering Arthosamid if you’ve tried exercise, weight loss, and other injections like Durolane or PRP. You need to understand that not all patients improve with Arthrosamid,
Dr Masci offers an Arthrosamid injection for £2400. He also treats patients from the USA and Canada. If you are interested in Arthrosamid, please get in touch with his dedicated team for further information.
Related conditions:
- Can osteoarthritis be reversed?
- What to do about no cartilage in the knee?
- Best injections for knee arthritis
- Durolane injection for arthritis
- PRP injection for knee arthritis
- Hyaluronic acid for arthritis and tendonitis
Could you please provide information of where the treatment is based. I am looking for options that are an alternative to knee replacement for my 75 year old mother.
I would also like more information about treatment for psyoratic arthritis for my daughter (in her feet) who is 26
Hi Rebecca, Arthrosamid is available in most EU countries and UK. I don’t think it’s licensed in US yet. You should see a rheumatologist to discuss treatment options for psoriatic arthritis.
LM
I had this procedure at a (different) clinic and cannot recommend it highly enough. To be able to walk without a stick and without pain after 8 years gave me my life back.
Thanks, Patricia, for the comment. As I mentioned in my blog, I’m still hesitant to recommend Arthrosamid as a first-line injeciton treatment as it’s a relatively new drug. But if I get more feedback like yours, I’ll be more confident moving forward. Indeed, my veterinary friends are raving about how effective Arthrosamid is in racing horses.
Lorenzo
Can you tell me if this is suitable for moderate/severe osteoarthritis of the patella femoral joint please.
Hi Pamela, patellofemoral osteoarthritis is generally less responsive to other injectables such as hyaluronic acid or PRP. So I tend to use Arthrosamid in these cases as a preference.
LM
My 85 year-old father had surgery on his left knee for a torn meniscus in the 1970s. (Just a few years later, when the right knee was worked on, the procedure medical technology had evolved and the procedure was arthroscopic.) He’s reached a point where cortisone injections don’t work. For really the first time, just a couple of days ago, he said he is actively considering a knee replacement. But he also remarked that signing up for a procedure that would involve four or months of painful rehab is a difficult proposition when “I don’t knowhow many months I have left.
I had a vague memory of there being new treatments, but in doing the research, it’s clear the United States is lagging behind the UK. The FDA approved a hydrogel by Contura called Bulkamid (2.5% polyacrylamide; 97.5% water) for urinary incontinence, but whether this is the exact same configuration as Arthrosamid under another name is not clear. In any event, getting updated passports and going on an international trip sounds much more appealing than invasive surgery and months of rehab. Does your clinic offer services to non-UK residents/citizens?
Hi Shawn,
Yes, I believe the hydrogel used for urinary incontinence is the same gel used for knee osteoarthritis.
And yes I see overseas patients at my clinic.
LM
I can vouch for Dr. Lorenzo. I consult him from outside the UK for my treatment plan and he’s given practical and useful advice for my chondromalacia patella. His blog also has easy to digest and up to date information on new developments.
Hi could you please advice.I’m 52 and have had none on bone in my right knee for over 2 years.I’ve had steroid injections but they don’t work anymore.
My Gp has just referred me to see an orthopaedic surgeon but I’m told I’m too young for knee replacement surgery.
I will have to wait 10 years?
I’ve lost a lot of weight hoping this will help with weight bearing on the joints.I’m in agony 24/7.
I have psoriatic arthritis but possibly rheumatoid as I don’t have psoriasis.
Please could you advise if I could have this injection.It’s my tight knee and I can’t even walk anymore without aids.
Thank you.
Hi Mary,
I would avoid further cortisone injections as recent evidence suggests that cortisone injections may accelerate arthritis progression.
You have a few options. I outline options in this blog:
https://sportdoctorlondon.com/no-cartilage-in-knee/
Durolane is my preferred first option for mild to moderate osteoarthritis
https://sportdoctorlondon.com/durolane-injection/
Arthrosamid is an option if your knee pain and swelling is NOT directly related to inflammatory arthritis. if you have acute inflammatory arthritis affecting your knee, you need to consider other options.
Hi, I had Arthrosamid injections in both knees 6 weeks ago, so far I’ve had no relief whatsoever, is there a chance it will improve? If not what should be my next step?
Hi Les, As I mentioned in my blog, onset of pain relief may take up to 12 weeks and sometimes longer. So you need to wait a few more months yet.
LM
Hello, Would insurance cover the injections? Thanks
Hi Cynthia,
Many thanks for your query. Unfortunately, UK private insurance does not cover Arthrosamid. Moreover, I’m not aware of insurance coverage in Europe. Currently, it is not used in the USA or Canada.
Regards
Lorenzo