Osteoarthritis is the most common form of arthritis affecting the knee joint. It is increasingly common among younger people. Treatment options include exercise, weight loss, medication, injections, and knee joint replacement. A new injection, Arthrosamid gel, shows greater promise than other injections for reducing knee arthritis pain. What is Arthrosamid UK, and how effective is it in knee osteoarthritis?     

Osteoarthritis

Osteoarthritis is a chronic condition commonly affecting the knee joint. It wears away the joint’s shock-absorbing cartilage, resulting in bone-on-bone contact. 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 intra-articular knee joint injections 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 has offered people an effective alternative to currently available injection therapies. 

What is Arthrosamid UK?

Arthrosamid UK is a new hydrogel material in which water molecules (97%) are 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 facial fillers, 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. 

More than 22,000 Arthrosmaid injections have been performed in Europe and the UK since the product’s 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 that lubricates and helps maintain joint health.

When hydrogel is injected into the knee joint, it is taken up by synovial cells and forms a new joint lining. This new lining reduces knee joint inflammation, thereby reducing pain. The gel also produces cushioning and lubrication. Forming a new joint lining can take up to four weeks. 

A New Laboratory study supports the 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 synovial cells lining the joint. These cells made a new ‘pseudo’ joint lining or barrier. 

Evidence in Knee Osteoarthritis 

First, two promising studies published about 15 years ago showed that hydrogel injected into arthritic knees produced excellent results starting at 4 weeks and continuing through 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 old) and slimmer patients, and in patients with a large effusion, Arthosamid performed better than hyaluronic acid.   In this study, Arthrosamid gel had an overall positive response rate of 73% in the 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 begins at 4 weeks and peaks at approximately 12 weeks. However, a recent study from Turkey suggests that the pain-free effect may take up to six months to reach its 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 persists longer than that of other injectables. Recently released longer-term data from RCTs suggest 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 is more effective than hyaluronic acid in treating a swollen knee.

An RCT comparing Arthrosamid to Synvisc-1 (hyaluronic acid) found that patients with knee joint swelling responded better to Arthrosamid at 6 months. If you have a swollen knee, consider Arthrosamid rather than hyaluronic acid to relieve pain and improve knee function in knee arthritis. We think patients with an inflamed knee joint and swelling tend to do better.   

How Do We Deliver Arthrosamid Injection?    

We inject this hydrogel directly into the knee joint. We strongly recommend that you perform this procedure under 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 reach the joint.

Generally, your doctor will administer a local anaesthetic to the skin. Then, your doctor will insert a needle with ultrasound guidance into the knee joint. If your knee has significant swelling, your doctor may drain it first. The hydrogel is injected directly into the joint through the needle. Your doctor must administer it using sterile technique. Please see the video below of Dr Masci using ultrasound guidance to inject the knee joint.    

What should you expect immediately after the procedure?    

Following the procedure, we will observe you for 15 minutes. You may experience 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 2-4 weeks, and occurs in 20% of patients. We manage a flare with reduced activity, regular ice packs, and oral anti-inflammatory agents 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 among more than 15,000 Arthrosamid injections. (0.02%). 

How Does Arthrosamid UK Differ from Other Injections?

Arthrosamid differs from other injectables, such as hyaluronic acid, PRP, or stem cells. The hydrogel is non-absorbable and remains in the joint longer, providing lubrication. Conversely, the body rapidly degrades hyaluronic acid and PRP, thereby limiting their effects and reducing their potency. 

Arthrosamid Injection UK Cost 

Dr Masci performs this injection for £2400. He performs this procedure with ultrasound guidance to improve accuracy. He has over 15 years of experience in ultrasound-guided procedures and teaches physicians and physiotherapists to perform injections under ultrasound guidance. 

Other Frequently Asked Questions:  

When can you return to sport after an Arthrosamid gel injection? 

Generally, we recommend that you rest your knee from exercise for approximately 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:

  • 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.
  • Day 3-7 post-injection: Continue upper body weight, swimming with light kicking, light cycling
  • Day 7-10 post-injection: Continue upper body weights, swimming, light cycling, and start lower body weights at 50% of the usual intensity. 
  • Day 14 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; therefore, the body rapidly degrades it. On the other hand, Arthrosamid hydrogel is nondegradable, meaning it remains in the knee joint longer.

Are there any contraindications to the use of 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 by 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 with Synvisc-1, a hyaluronic acid-based product. 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 recommend waiting until the Durolane has been fully degraded before administering Arthrosamid. We recommend waiting 3 months to allow the Durolane to degrade fully. 

Can Arthrosamid gel be injected without imaging?   

Yes, but we don’t recommend it. We know that ultrasound improves the accuracy of knee joint injections. For example, studies suggest that knee injections without ultrasound are only 60-80% accurate compared to ultrasound-guided injections, which are 100% accurate. If you’re considering Arthrosamid, ensure it is injected under ultrasound guidance. 

Why are prophylactic antibiotics recommended?   

Because Arthrosamid is nondegradable, you must use antibiotics. A high antibiotic concentration at the time of 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 observed at 3 months, but it may take longer to develop. In a recent study from Turkey, the positive effects may take up to six months to reach their maximum impact. 

How much does Arthrosamid reduce pain and improve knee function? 

Arthrosamid improves pain and function by an average of 20-25%. 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 2025 study shows that Arthrosamid lasts for at least 5 years. In this dataset, patients younger than 70 years showed a better response than those older than 70. 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 collecting more data to identify who responds best to the drug. 

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 be available in the USA?

Contura has applied for FDA approval and is well into the process of getting Arthrosamid approved in the United 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 extend to approximately 15 years, with 90 knees undergoing knee replacement after Arthrosamid. This cohort has had no reports of problems during or after the knee replacement.

Do higher-risk patients, such as those with diabetes or obesity, have a different response? 

Perhaps. The effectiveness of Arthrosamid drops is approximately 10% lower than in 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 can also help alleviate pain. 

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 show that about 5-20% of patients can have worse scores after an Arthrosamid injection. This data is not unlike that of other injectables, such as hyaluronic acid, PRP, or stem cells. Worsening scores may be due to deteriorating arthritis rather than the Arthrosamid. 

Can I receive treatment for both my knees? 

Yes. However, as a general rule, we recommend spacing injections by at least 1 week and avoiding them at the same consultation. 

If I have a partial positive effect from Arthrosamid, can I have a top-up injection? 

Yes, but we recommend waiting approximately 6 months before receiving a top-up injection, as Arthrosamid may take up to 6 months to take full effect. Top-up injections are usually 3 mL, compared with 6 mL for the initial injection. 

Which patients respond better to Arthrosamid? 

From our experience, patients who may be better suited to Arthrosamid include: 

  • Patellofemoral osteoarthritis patients who want to avoid surgery.
  • Those who have tried other injections but have not managed to get long-term pain relief
  • Too young or not ready to have an arthroplasty > sub70 have an 80%+ response rate
  • Those who want to remain active
  • Those who present with a swelling effusion and or history of pain following activity.

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.  

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