Knee Injection Comparison
Arthrosamid® vs
PRP for Knee OA
Two very different approaches to knee osteoarthritis — one a permanent hydrogel cushion, the other an autologous biologic. Here is the honest comparison from London Cartilage Clinic.
Reviewed byProf Paul Lee MBBch, FRCS (Tr & Orth), PhDLast reviewed 1 May 2026Quick Answer
PRP (platelet-rich plasma) is an autologous biologic injection that aims to modulate the joint environment; for knee osteoarthritis the published evidence is mixed and duration is typically months. Arthrosamid® is a non-resorbable polyacrylamide hydrogel with published outcome data showing on average two to three years of symptom relief from a single injection in suitable patients. PRP may suit some early-stage cases; Arthrosamid® is generally the more durable choice for established osteoarthritis.
The Headline Difference
Arthrosamid® vs PRP — the key difference
PRP is a biologic — your own blood, processed to concentrate platelets, injected back into the joint. Arthrosamid® is a non-biologic, non-resorbable hydrogel that physically cushions the joint long-term. PRP aims to modulate biology over months; Arthrosamid® aims to relieve symptoms mechanically over years. These are two different goals, and the right answer depends on which one matches your case.
Mechanism of Action
How each treatment works
Arthrosamid® is a polyacrylamide hydrogel injected into the knee joint under ultrasound guidance. The gel integrates into the synovial membrane, acting as a long-term cushion. It is not absorbed, not metabolised and not regenerative.
Mechanism of action is mechanical — physical cushioning and lubrication — rather than biological.
PRP is prepared by taking a venous blood sample, processing it in a centrifuge to concentrate platelets and growth factors, then injecting the concentrate back into the joint, typically under ultrasound guidance.
The biological hypothesis is that concentrated platelets release growth factors that modulate the joint environment, reduce inflammation and may support cartilage health. Evidence quality in knee OA is variable.
How Long Results May Last
Duration and number of injections
2 to 3 years
Months, typically
PRP evidence in knee osteoarthritis is more heterogeneous than for Arthrosamid®. Outcomes depend on preparation method, leukocyte content and patient selection. We will discuss what to expect for your specific case at consultation.
Treatment Course
Number of injections
One injection is the standard treatment course in suitable patients. Most cases are treated with a single box per joint.
PRP is commonly delivered as a course of two to three injections spaced over weeks, followed by repeat courses every six to twelve months for ongoing benefit. Single-injection protocols also exist.
Safety and Infection
Safety considerations
Both treatments are delivered under ultrasound guidance at London Cartilage Clinic. The most serious risk for either is joint infection, which is rare. PRP carries a marginally lower infection risk because it uses an autologous product without external additives, but the difference is small in absolute terms.
Arthrosamid® uses a non-resorbable hydrogel, so a late infection is harder to manage than for resorbable injections. This is why we use routine IV antibiotic cover for Arthrosamid® specifically.
See Arthrosamid® infection risk and prevention and Arthrosamid® side effects and safety.
Patient Selection
Who each treatment may suit
PRP is often considered for earlier-stage knee osteoarthritis where the goal is to modulate the joint environment alongside conservative care. Arthrosamid® tends to suit patients with established osteoarthritis who want longer duration from a single injection and are looking to delay more invasive treatment.
Neither treatment regenerates cartilage. Neither is a substitute for knee replacement where replacement is clinically appropriate. See who is suitable for Arthrosamid? for the full framework.
Cost and Value
What each treatment costs
At London Cartilage Clinic, Arthrosamid® costs from £3,000 for one box, inclusive of consultation, ultrasound, the product, the fifteen-step injection protocol and the six-week follow-up. See the Arthrosamid® cost guide for full pricing.
PRP pricing depends on the protocol (single injection vs course), processing system used, and whether ultrasound guidance is included. A full PRP course can cost a meaningful fraction of an Arthrosamid® injection, and repeat courses every six to twelve months accumulate. Over a two-to-three-year window, total spend can be similar.
Our Honest Take
When we may recommend each
You have established knee osteoarthritis with mild-to-moderate cartilage wear.
You want longer-duration symptom control from a single injection and a clear single treatment plan.
You want to delay more invasive surgery when appropriate, with realistic expectations and willingness to accept the safety protocol.
You are at an earlier stage of knee osteoarthritis or have a sports-medicine type presentation where biologic modulation is the goal.
You prefer an autologous biologic and are willing to accept variable evidence quality and shorter duration.
You want to avoid a permanent intra-articular implant.
When Each Is The Wrong Answer
When we would not recommend each
End-stage bone-on-bone arthritis where Arthrosamid® is unlikely to deliver meaningful benefit.
Active infection or unwillingness to accept the conservative safety protocol.
Unrealistic expectation of cure, regeneration or guaranteed permanent relief.
End-stage knee arthritis where PRP is unlikely to deliver meaningful benefit.
Patients who want a single, multi-year intervention rather than repeat biologic courses.
Where prior PRP has not delivered useful benefit, repeating may not be the right next step.
The Bottom Line
In summary
For established knee osteoarthritis where the goal is durable symptom control from a single injection, Arthrosamid® has the stronger evidence base and longer duration. PRP can be a reasonable choice for earlier-stage cases or where an autologous biologic is preferred, but expect shorter duration and potentially repeat courses. The right answer for any individual is decided at consultation with imaging review.
Arthrosamid® vs PRP
Frequently asked questions
Is PRP better than Arthrosamid® for knee arthritis?
Not better or worse — different. PRP is a biologic intervention with months of duration and variable evidence in knee OA. Arthrosamid® is a non-resorbable hydrogel with multi-year duration from a single injection. The right choice depends on stage of disease, patient goals and expectations.
Can I have Arthrosamid® after PRP?
Yes, prior PRP is not a contraindication to Arthrosamid®. We will review your imaging and clinical picture; in most cases, a switch to Arthrosamid® is appropriate when PRP has not delivered the expected duration or when longer-acting symptom control is the goal.
Does the NHS offer PRP or Arthrosamid®?
Neither is routinely funded by the NHS for knee osteoarthritis. Both are accessed privately at London Cartilage Clinic. See the Arthrosamid® funding and insurance page for detail.
How does PRP evidence compare to Arthrosamid® evidence?
PRP evidence in knee OA is more heterogeneous — published trials show benefit in some patients and not others, partly because PRP preparations differ widely. Arthrosamid® evidence is more consistent in showing multi-year symptom relief from a single injection in suitable patients. Read more on the Arthrosamid® clinical evidence page.
Can I have both PRP and Arthrosamid® in the same knee?
In principle yes, but rarely as a combined protocol. We typically choose the most appropriate single treatment based on the imaging, clinical picture and patient goals discussed at consultation.
Book an Arthrosamid® Assessment – London
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Learn More about Arthrosamid
Deep dive into our clinical resources and patient guides.
Cost in the UK
Arthrosamid® cost in the UK from £3,000, what is included and why prices vary.
NHS & Insurance
Is Arthrosamid® available on the NHS or private insurance?
Suitability
Who is suitable for Arthrosamid® — and who may need caution.
Clinical Evidence
Real-world outcome data and what the evidence means for patients.
Side Effects & Safety
Arthrosamid® side effects, risks, complications and clinical context.
Infection Risk
Arthrosamid® infection risk, prevention protocol and IV antibiotic policy.
In London
Private Arthrosamid® treatment at our Harley Street clinic.
Self-Assessment
Eight-question Arthrosamid® suitability self-assessment tool.
Full FAQ
Arthrosamid® patient FAQ across cost, suitability, safety and comparisons.
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vs Knee Replacement
Where Arthrosamid® may help delay surgery — and where it cannot.
Arthrosamid® Injection
Comprehensive Overview
Arthrosamid® is a registered trademark of Contura A/S. London Cartilage Clinic is not affiliated with or endorsed by Contura A/S.