Knee Injection Comparison
Arthrosamid® vs
PRP for Knee OA
Two very different approaches to knee osteoarthritis—one a non-absorbable hydrogel, the other an autologous biologic. Here is the honest comparison from London Cartilage Clinic.
Reviewed byProfessor Paul YF Lee MBBch, FRCS (Tr & Orth), PhDCartilage and joint preservation expertiseQuick 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 evidence and protocols vary. Arthrosamid® is a non-resorbable polyacrylamide hydrogel with observational group outcomes reported through 24 months. There is insufficient comparative evidence to say one is universally better; diagnosis, prior response and patient preferences matter.
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. PRP aims to influence the joint environment; Arthrosamid® is intended for symptom management through a different material pathway. These are two different goals, and the 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 and is intended to remain in the joint. It is 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
Observed to 24 months
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 includes joint infection. This page does not claim a comparative incidence without suitable head-to-head evidence. Sterile technique and image guidance do not eliminate risk.
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 are willing to discuss a non-absorbable single-injection option. Arthrosamid is not proved to delay surgery.
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. Compare the actual recommended PRP preparation and course rather than assuming either treatment's repeat schedule or duration.
Our Honest Take
When we may recommend each
You have established knee osteoarthritis with mild-to-moderate cartilage wear.
You want to discuss a non-absorbable single-injection option and a clear treatment plan.
You understand that symptom management is not proved to delay surgery and accept the product-specific 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 non-absorbable material intended to remain in the joint.
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
Arthrosamid and PRP differ in material, preparation, evidence and treatment course. The Arthrosamid cohort is observational and PRP evidence is heterogeneous; neither makes an individual outcome predictable. The choice is made after diagnosis, imaging review, prior treatment history and discussion of a non-absorbable product versus an autologous injection.
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 observational group outcomes reported through 24 months. The right choice depends on diagnosis, evidence limits, patient goals and risk preferences.
Can I have Arthrosamid® after PRP?
Prior PRP is not automatically a contraindication, but it does not establish that Arthrosamid is suitable. We review the diagnosis, imaging, clinical picture, prior response and product-specific risks before recommending another injection.
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 includes the 24-month prospective observational cohort. No direct trial used here establishes that one treatment is universally superior. 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.
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