Arthrosamid

What is Arthrosamid?

Arthrosamid is an injectable polyacrylamide hydrogel.

It is made from:

• 97.5% water
• 2.5% cross-linked polyacrylamide

Unlike hyaluronic acid, the hydrogel is not gradually broken down or absorbed by the body. It is classed as a non-biodegradable injectable implant and remains within the tissues of the knee. 

The standard treatment involves a total of 6 ml injected into the knee joint.

How does Arthrosamid work?

Arthrosamid is injected into the synovial cavity of the knee.

Following treatment, the hydrogel becomes incorporated into the synovial lining, which is the soft tissue covering the inside of the joint capsule.

The precise way in which this leads to a reduction in pain is still being studied. The treatment is intended to alter the physical properties of the synovial lining and may reduce symptoms associated with knee osteoarthritis.

It does not act as a joint replacement, rebuild cartilage or remove the structural changes caused by arthritis.

Who might Arthrosamid be considered for?

Arthrosamid may be discussed with adults who have knee osteoarthritis causing ongoing pain, stiffness or reduced function.

It may be considered where:

• Symptoms continue despite exercise and other non-operative treatments
• Other injection options have already been discussed or tried
• Pain is limiting walking, activity or rehabilitation
• The patient does not currently want, need or qualify for surgery
• There is a clear diagnosis of symptomatic knee osteoarthritis

The treatment is only intended for the knee. It is not currently used as a general injection for tendon problems, sports injuries or osteoarthritis in other joints.

How is Arthrosamid different from other injections?

Arthrosamid does not contain a corticosteroid, hyaluronic acid or blood-derived platelets.

Unlike Cingal or Monovisc, it is not absorbed over time. It remains in the knee as a permanent implant.

This is an important distinction and should be considered when comparing it with other treatments. The potential benefits, limitations and permanent nature of the material will be explained before treatment is recommended.

What happens during treatment?

Arthrosamid is given as a single treatment into the affected knee.

Before the procedure, preventative antibiotics are required to reduce the risk of infection. Local anaesthetic is used around the injection site, and the knee is cleaned carefully using a sterile technique. 

The hydrogel is then injected into the knee joint. Ultrasound guidance may be used to confirm accurate placement.

If there is a significant amount of fluid within the knee, this may be removed before the injection where clinically appropriate.

What happens after the injection?

Some discomfort, swelling or stiffness can occur following treatment.

Patients are usually advised to keep activity relatively light immediately afterwards and then return gradually to normal movement. Dr Jones will provide specific advice based on the condition of the knee and the procedure performed.

Arthrosamid does not usually produce immediate pain relief. Any improvement is expected to develop gradually over the following weeks.

How long can the effect last?

Clinical studies have reported improvements in pain and function for some patients following a single Arthrosamid treatment.

Follow-up studies have reported benefits continuing beyond one year in patients who responded to treatment. However, individual results vary, and not every patient experiences a meaningful improvement. Much of the available research has involved relatively small patient groups and studies without a direct comparison treatment. 

NICE considered Arthrosamid for guidance development but did not select it, stating that there was insufficient evidence at that stage. This does not mean the treatment cannot be offered privately, but it reflects the current limitations of the evidence base. 

Does Arthrosamid last permanently?

The hydrogel itself is non-biodegradable and is intended to remain permanently within the knee.

This does not mean that symptom relief is guaranteed to last permanently. Osteoarthritis may continue to change, and pain can be influenced by several structures within and around the knee.

Some patients may experience a sustained improvement, while others may have a smaller response or no meaningful benefit.

Can Arthrosamid be repeated?

Arthrosamid is normally offered as a single treatment.

Because it remains within the knee, repeat treatment is not approached in the same way as repeat corticosteroid or hyaluronic acid injections.

Any further injection treatment would require careful review of the previous response, the condition of the knee and the presence of an existing non-absorbable implant.

When might Arthrosamid not be suitable?

Arthrosamid should not be injected where there is:

• An infection or active skin condition around the knee
• An infected or severely inflamed knee joint
• A previous non-absorbable injectable implant in the same knee
• A recently administered absorbable joint injection that has not yet been absorbed

Other medical conditions, medication and previous knee procedures will also need to be considered. 

What are the possible risks?

Possible risks include:

• Temporary pain, swelling or stiffness
• Bruising or bleeding
• Infection
• An inflammatory reaction
• No meaningful reduction in symptoms
• A result that does not meet the patient’s expectations

Because Arthrosamid remains within the joint, avoiding infection is particularly important. This is why antibiotic cover and careful sterile technique form part of the treatment process.

The full benefits, risks and alternatives will be discussed before consent is taken.

A treatment option within a wider plan

Arthrosamid is one of several possible treatments for knee osteoarthritis.

Other options may include exercise, physiotherapy, weight management, medication, bracing, corticosteroid injections, hyaluronic acid injections, PRP or surgery.

The purpose of the consultation is not simply to decide whether Arthrosamid can be injected. It is to consider whether it is the most appropriate option at that stage of the condition.

Is Arthrosamid right for me?

Before recommending Arthrosamid, Dr Jones will assess the knee, review any relevant imaging and consider what treatment has already been tried.

He will explain:

• What the injection is intended to achieve
• The permanent nature of the hydrogel
• The limitations of the current evidence
• The possible risks
• The alternative treatment options
• What may happen if no injection is undertaken

The decision to proceed will be made after a balanced discussion based on the condition of the knee and the patient’s individual priorities.