A Scientific Guide to Patient Selection, Osteoarthritis Stage and Alternatives to Knee Replacement

For many people with knee osteoarthritis, the most important question is not simply:

“Does Arthrosamid work?”

The more useful question is:

“Is Arthrosamid the right treatment for my particular knee?”

This distinction matters.

Knee osteoarthritis is not the same disease in every patient. Two people of the same age can have completely different causes of pain, different levels of cartilage loss, different knee alignment, different levels of inflammation and very different expectations from treatment.

For this reason, an injection should never be selected like a product from a catalogue.

The success of any intra-articular treatment depends heavily on selecting the right treatment for the right patient at the right stage of disease.

Arthrosamid® is one of the newer long-acting non-surgical options available for symptomatic knee osteoarthritis. Clinical studies now include patients with moderate and advanced radiographic osteoarthritis, including Kellgren–Lawrence Grades 2, 3 and 4.

However, radiological grade alone does not decide whether Arthrosamid is appropriate.

A proper decision should combine:

• symptoms,
• clinical examination,
• weight-bearing X-rays,
• knee alignment,
• joint stability,
• range of movement,
• previous treatment response,
• activity level,
• body weight and metabolic factors,
• and, importantly, the patient’s own goals and expectations.

This is why the first step should be an orthopaedic assessment — not simply booking an injection.

What Is Arthrosamid?

Arthrosamid is a 2.5% cross-linked polyacrylamide hydrogel (PAAG) containing approximately 97.5% sterile water.

It is injected directly into the knee joint.

Unlike conventional hyaluronic acid injections, the hydrogel is non-biodegradable and non-absorbable.

It becomes integrated into the synovial tissue lining the joint and is designed to provide prolonged symptomatic improvement.

The treatment is intended for adults with symptomatic knee osteoarthritis.

The treatment typically involves approximately 6 mL per knee, administered intra-articularly by an appropriately trained physician.

Current manufacturer information specifies a recommended dose of 6 mL.

Arthrosamid is not:

• a steroid,
• PRP,
• a stem-cell treatment,
• a cartilage transplant,
• or a medication that grows new cartilage.

Its role is principally to improve pain and function in an osteoarthritic knee.

Which Stage of Knee Osteoarthritis Is Arthrosamid Suitable For?

This is probably the most important question.

Knee osteoarthritis is often described radiographically using the Kellgren–Lawrence (KL) grading system.

Very broadly:

KL Grade 1

Very early or doubtful radiographic osteoarthritis.

KL Grade 2

Definite but relatively mild osteoarthritis with osteophyte formation and possible early joint-space narrowing.

KL Grade 3

Moderate osteoarthritis with clearer joint-space narrowing, osteophytes and structural change.

KL Grade 4

Advanced osteoarthritis with severe joint-space loss, significant structural deterioration and often “bone-on-bone” disease.

Current clinical evidence for polyacrylamide hydrogel includes patients with KL Grades 2–4, meaning Arthrosamid should not automatically be considered only an “early arthritis” treatment.

However, the probability and purpose of treatment may be different at different stages.

Arthrosamid in Mild Osteoarthritis

A patient with very early knee osteoarthritis does not necessarily need Arthrosamid simply because some degenerative change appears on an MRI or X-ray.

For mild disease, treatment should first consider the overall clinical picture.

Depending on the patient, appropriate management may include:

• exercise therapy,
• quadriceps and hip strengthening,
• weight management where relevant,
• biomechanical correction,
• physiotherapy,
• activity modification,
• appropriate analgesic or anti-inflammatory treatment,
• and management of contributing factors.

If symptoms remain significant despite appropriate conservative treatment, intra-articular treatment may then be considered.

In other words:

Earlier disease does not automatically mean “inject earlier”.

The decision depends on symptoms and functional limitation, not imaging alone.

Arthrosamid in Moderate Knee Osteoarthritis

Patients with established symptomatic KL Grade 2–3 osteoarthritis may represent an important group in whom Arthrosamid can be considered.

These are often patients who:

• have persistent pain despite conservative treatment,
• experience difficulty walking or climbing stairs,
• have reduced ability to exercise,
• have pain interfering with work or daily activities,
• are not yet clear candidates for knee replacement,
• or would prefer to continue non-surgical management.

Clinical trials of PAAG have demonstrated improvement in pain and function in patients with moderate-to-severe knee osteoarthritis.

Long-term follow-up studies have reported sustained improvements following a single 6 mL intra-articular treatment in some patients for periods extending up to five years.

However, individual response varies.

No responsible physician should promise that every patient will obtain the same duration or degree of benefit.

Can Arthrosamid Be Used in Grade 4 or “Bone-on-Bone” Arthritis?

Potentially, yes.

Grade 4 osteoarthritis is not automatically an exclusion.

Recent PAAG studies have included patients with KL Grade 4 disease, and symptomatic improvement has been observed in some patients with advanced osteoarthritis.

However, this is where patient selection becomes particularly important.

A Grade 4 knee with relatively preserved alignment and movement is very different from a Grade 4 knee with:

• severe varus or valgus deformity,
• major instability,
• severe flexion contracture,
• profound restriction of movement,
• substantial bone loss,
• disabling pain,
• or major functional deterioration.

An injection cannot mechanically realign a badly deformed knee.

It cannot correct major ligamentous instability.

It cannot rebuild a destroyed joint surface.

Therefore, in advanced disease, the surgeon must determine whether the patient’s symptoms can realistically be improved with non-surgical treatment or whether joint replacement offers the more appropriate and predictable solution.

Recent observational evidence also suggests that patients with lower KL grades may have a greater probability of achieving clinically meaningful improvement, while patients with higher-grade disease are more likely subsequently to proceed to total knee replacement.

This does not mean Arthrosamid cannot work in Grade 4.

It means expectations must be realistic.

Can Arthrosamid Delay Knee Replacement?

This question needs careful wording.

Arthrosamid should not be described as a substitute for knee replacement.

Knee replacement and Arthrosamid treat fundamentally different situations.

A total knee replacement physically replaces severely damaged joint surfaces.

Arthrosamid is a non-surgical treatment designed primarily to improve osteoarthritis symptoms and function.

However, there is an important group of patients between these two extremes.

For example:

A patient may have significant osteoarthritis but still be functioning reasonably well.

They may not yet have a strong surgical indication.

They may wish to postpone major surgery because of work, family responsibilities or travel.

They may have medical reasons for preferring non-operative management.

Or they may simply want to exhaust appropriate non-surgical options before proceeding to arthroplasty.

In an appropriately selected patient, successful symptom control with Arthrosamid may allow the patient to continue functioning without immediately progressing to knee replacement.

That can effectively extend the period during which the knee can be managed non-operatively.

However, it would be scientifically incorrect to promise:

“Arthrosamid will delay your knee replacement for five years.”

Long-term studies demonstrate sustained symptom improvement in some patients, but they do not establish a guaranteed number of surgery-free years for every patient.

Who Appears More Likely to Benefit?

Patient-selection research is beginning to provide useful information.

A 2025 prospective cohort involving more than 300 treated knees found better clinical outcomes to be associated with factors including:

• lower radiographic osteoarthritis grade,
• lower BMI for some pain outcomes,
• better baseline functional status,
• increasing age in one responder analysis,
• and absence of diabetes in one multivariable analysis.

These results are interesting, but they should not be turned into rigid rules.

For example:

An older patient is not automatically a better candidate than a younger patient.

Similarly:

A patient with diabetes is not automatically unsuitable.

These are statistical associations from observational research, not absolute inclusion or exclusion criteria.

The individual knee still has to be assessed.

Is There an Age Limit for Arthrosamid?

There is no simple age at which Arthrosamid suddenly becomes suitable or unsuitable.

Chronological age is only one factor.

Consider two patients:

Patient A

55 years old, severe Grade 4 medial compartment OA, major varus deformity, instability and severe loss of function.

Patient B

72 years old, symptomatic Grade 3 OA, reasonably preserved alignment, good mobility and a strong preference to remain active without surgery.

The younger patient is not necessarily the better injection candidate.

In fact, Patient B may potentially have the more suitable knee for a non-surgical intervention.

The decision should therefore focus on the condition of the knee rather than the number on the patient’s passport.

Does Body Weight Matter?

Body weight can influence knee osteoarthritis in several ways.

Higher body weight increases mechanical load across the joint and may also contribute to systemic metabolic and inflammatory processes associated with osteoarthritis.

Recent PAAG observational data found lower BMI to be associated with better pain outcomes at follow-up.

However, obesity should not automatically exclude treatment.

Instead, weight should form part of a broader assessment.

For some patients, combining symptom treatment with weight management and strengthening may produce a substantially better long-term result than relying on an injection alone.

Why the X-Ray Is So Important

Many patients send an MRI and assume that MRI alone decides treatment.

For osteoarthritis, this is not always the case.

Weight-bearing knee X-rays can be extremely important.

They can demonstrate:

• joint-space narrowing,
• compartment involvement,
• osteophytes,
• bone changes,
• overall disease severity,
• and, with appropriate views, mechanical alignment.

Because the knee functions under load, standing radiographs often provide information that cannot be obtained from a standard supine MRI alone.

Do I Need an MRI Before Arthrosamid?

Not necessarily.

MRI can be valuable when:

• symptoms do not match the X-ray,
• a meniscal lesion is suspected,
• there has been trauma,
• ligament pathology is suspected,
• subchondral pathology is possible,
• osteonecrosis is being considered,
• or another diagnosis needs to be excluded.

But an MRI should not automatically be ordered simply because a patient wants an injection.

For many established osteoarthritis cases, a good clinical examination combined with appropriate weight-bearing radiographs may provide the information needed.

The Most Important Rule: Imaging Must Match the Patient

One of the biggest mistakes in knee treatment is treating the image rather than the patient.

A severe-looking MRI does not always mean severe symptoms.

Likewise, a relatively modest X-ray abnormality does not always explain substantial pain.

The orthopaedic assessment needs to answer:

Is osteoarthritis actually the main cause of this patient’s pain?

If the answer is no, injecting the knee simply because osteoarthritis appears on imaging may produce disappointing results.

When Arthrosamid May Not Be the Correct Treatment

Not every painful knee should receive an osteoarthritis injection.

Alternative causes of knee pain may include:

• symptomatic meniscal pathology,
• ligament injury or instability,
• inflammatory arthritis,
• acute synovitis,
• infection,
• osteonecrosis,
• stress or insufficiency fracture,
• patellofemoral disorders,
• significant malalignment,
• referred pain from the hip or spine,
• or other structural pathology.

For this reason, the diagnosis should be confirmed before treatment.

Arthrosamid Should Not Be Used in an Infected or Severely Inflamed Joint

According to current manufacturer safety information, Arthrosamid should not be injected when:

• there is an active skin disease or infection at or near the injection site,
• the knee joint is infected,
• the knee is severely inflamed,
• or a previous biodegradable intra-articular product remains present and has not yet been expected to absorb.

Clinical assessment is therefore essential before treatment.

Arthrosamid Compared With Hyaluronic Acid

Hyaluronic acid is probably the most relevant conventional injectable comparator because both are intra-articular treatments used for symptomatic osteoarthritis.

However, they are not the same product.

Hyaluronic acid is biodegradable and is eventually cleared.

Arthrosamid is a non-biodegradable polyacrylamide hydrogel.

A randomised controlled trial comparing a single 6 mL PAAG injection with hyaluronic acid found PAAG to provide comparable symptomatic benefit over one year.

Subsequent follow-up of the PAAG group has demonstrated sustained improvements extending to several years.

It is also important to recognise that recommendations regarding hyaluronic acid vary considerably between guidelines.

For example, NICE does not currently recommend intra-articular hyaluronan for routine osteoarthritis management, and the AAOS does not recommend routine use for symptomatic knee OA.

This illustrates an important point:

The fact that two treatments are both called “knee injections” does not mean they have the same evidence, mechanism or appropriate patient population.

Arthrosamid Compared With Corticosteroid Injection

Corticosteroid injections have a different clinical purpose.

They are primarily used for their anti-inflammatory effect and can provide short-term pain relief.

Current NICE guidance describes the expected benefit of intra-articular corticosteroid injection as short-term, approximately 2–10 weeks.

AAOS similarly recognises corticosteroid injections primarily as an option for short-term symptom improvement.

Arthrosamid is not intended to act as a short-duration anti-inflammatory steroid injection.

Its clinical proposition is longer-term symptomatic management.

Therefore, deciding between the two depends on what the physician is trying to achieve.

What About PRP?

PRP belongs to a different treatment category.

It is prepared from the patient’s own blood and is considered an orthobiological treatment.

PRP should therefore not be viewed as the direct equivalent of Arthrosamid.

Depending on age, osteoarthritis phenotype, disease stage and treatment goals, PRP may still be considered in certain patients.

But asking:

“Is PRP better than Arthrosamid?”

is often less useful than asking:

“Which treatment mechanism is most appropriate for this particular knee?”

Why One Injection Can Work for One Patient and Fail in Another

This is one of the most important concepts for patients to understand.

An injection can be technically perfect and still produce a disappointing result if the wrong problem is being treated.

For example:

A patient with stable moderate osteoarthritis and preserved alignment may have a very different chance of benefit from a patient with:

• severe deformity,
• instability,
• profound joint destruction,
• untreated mechanical pathology,
• or pain arising from another source.

This is why successful injection therapy is customised medicine.

The product alone does not determine the result.

Patient selection matters enormously.

How Much Arthrosamid Is Used?

Arthrosamid is supplied in sterile pre-filled 1 mL syringes.

Treatment typically uses a total of approximately 6 mL per treated knee, which corresponds to the manufacturer’s currently recommended dose.

The treating physician determines the injection technique according to the individual knee and clinical circumstances.

More product should not automatically be interpreted as better treatment.

Can Arthrosamid Be Repeated?

Early PAAG research included treatment protocols involving more than one administration, whereas the current Arthrosamid treatment protocol is based around a single 6 mL intra-articular treatment.

Because Arthrosamid is non-biodegradable and remains within the joint, repeat treatment should not be approached in the same way as routinely repeating an absorbable injection.

If symptoms recur or response is inadequate, the knee should first be reassessed.

The appropriate next step may be:

• continued conservative management,
• another type of treatment,
• further investigation,
• or surgery.

Repeat treatment should therefore be determined by the treating specialist rather than automatically scheduled.

How Long Can Arthrosamid Work?

Current long-term clinical studies have followed patients for up to five years after a single 6 mL injection.

In these studies, improvements in:

• WOMAC pain,
• stiffness,
• physical function,
• and patient global assessment

were maintained in groups of patients through long-term follow-up.

This is encouraging evidence.

However, several limitations need to be understood.

Not every original study participant completed five-year follow-up.

Long-term extension studies are also not the same as five-year placebo-controlled randomised trials.

Therefore, the scientifically correct conclusion is:

Arthrosamid has evidence of sustained symptom improvement for up to five years in some treated populations.

It is not correct to say:

“One injection lasts five years in everyone.”

Does Arthrosamid Regenerate Cartilage?

No.

There is currently no basis for telling patients that Arthrosamid regrows cartilage destroyed by osteoarthritis.

Patients may experience major improvements in pain or function without structural cartilage regeneration.

Symptomatic improvement and cartilage regeneration are not the same thing.

Does Arthrosamid Cure Osteoarthritis?

No.

Knee osteoarthritis is a chronic joint disorder involving cartilage, bone, synovium, muscles and biomechanics.

Arthrosamid can be part of its management.

It does not remove the underlying diagnosis.

Good long-term treatment may still include:

• appropriate exercise,
• strengthening,
• weight management,
• physical therapy,
• biomechanical treatment,
• activity optimisation,
• and periodic orthopaedic review.

So Who Is a Good Arthrosamid Candidate?

A reasonable candidate may be an adult with:

• confirmed symptomatic knee osteoarthritis,
• persistent pain or functional limitation,
• symptoms that correlate with clinical and radiological findings,
• insufficient improvement from appropriate conservative management,
• a desire to pursue non-surgical management,
• and a knee in which the surgeon believes an intra-articular treatment has a reasonable chance of producing meaningful benefit.

Moderate OA may often represent a logical treatment window.

Selected patients with advanced OA can also be considered.

Who May Be a Poor Candidate?

Arthrosamid may be less likely to provide the desired result when the dominant problem is:

• major mechanical deformity,
• severe instability,
• advanced structural destruction where arthroplasty is clearly indicated,
• another untreated source of knee pain,
• active infection,
• severe joint inflammation,
• or unrealistic expectations of what an injection can achieve.

The purpose of assessment is therefore not merely to determine whether an injection can technically be performed.

It is to decide whether it should be performed.

Should I Have Arthrosamid or Knee Replacement?

This decision should not be based on X-ray grade alone.

Knee replacement becomes an important consideration when there is advanced structural disease associated with substantial pain and loss of function despite appropriate non-operative management.

If a patient has a clearly arthritic but still functional knee and wishes to pursue further non-operative treatment, Arthrosamid may be considered.

If the knee has reached the point where mechanical destruction is the dominant problem and replacement is medically appropriate, repeated injections may simply postpone the treatment most likely to restore function.

Good medicine is not about avoiding surgery at all costs.

It is about performing the right treatment at the right time.

Every Arthrosamid Decision Should Be Individualised

There is no single algorithm that says:

Grade 2 = Arthrosamid

Grade 3 = Arthrosamid

Grade 4 = replacement

Real patients are more complicated.

Before recommending treatment, the orthopaedic specialist should consider:

1. Clinical symptoms
2. Duration of symptoms
3. Functional limitation
4. Physical examination
5. Weight-bearing X-rays
6. Osteoarthritis grade
7. Knee alignment
8. Stability
9. Range of movement
10. BMI and relevant comorbidities
11. Previous physiotherapy
12. Previous injections
13. Previous surgery
14. MRI findings where clinically relevant
15. Patient age and activity level
16. Patient expectations
17. Whether the patient is willing or medically suitable for surgery

Only then can a meaningful treatment decision be made.

Considering Arthrosamid in Antalya, Turkey?

For international patients, travelling abroad simply to obtain an injection before establishing whether the treatment is appropriate makes little medical sense.

Healing Journey follows a different approach.

Before travelling, patients can provide:

• weight-bearing knee X-rays where available,
• MRI images or reports,
• previous orthopaedic reports,
• details of previous injections,
• previous operations,
• current medications,
• and a description of their symptoms and functional limitations.

The case can then be reviewed to determine which orthopaedic pathway is most appropriate.

This may include Arthrosamid.

But it may also mean that another treatment is more suitable.

The objective is not to sell every patient the same injection.

The objective is to identify the right treatment for that particular knee.

The Bottom Line

Arthrosamid is a promising long-acting non-surgical treatment for symptomatic knee osteoarthritis, supported by clinical studies including patients with moderate and advanced disease.

Evidence currently extends into patients with Kellgren–Lawrence Grades 2–4.

However, the best outcomes do not depend on radiographic grade alone.

Patient selection matters.

Clinical examination matters.

Weight-bearing X-rays matter.

Alignment and stability matter.

Body weight and general health can matter.

Previous treatments matter.

And the patient’s expectations matter.

For some patients, Arthrosamid may provide meaningful long-term symptom control and help them continue managing their knee without immediately proceeding to surgery.

For others, physiotherapy, another injection strategy or knee replacement may be more appropriate.

The most successful knee injection is not necessarily the newest injection. It is the treatment correctly matched to the individual patient.

Considering Arthrosamid?

If you are considering Arthrosamid treatment in Turkey, you can send your existing knee X-rays, MRI and medical reports for orthopaedic review before travelling.

The first question we aim to answer is not simply whether Arthrosamid can be injected.

It is:

Is Arthrosamid genuinely the right treatment for your knee?