Why these two injections are not direct competitors

Patients researching ChondroFiller and Arthrosamid often arrive at the same question: which one should I choose? In most cases, that framing is not quite right — because the two injections are not competing for the same job. What the MRI shows, not personal preference, is the primary factor that determines which treatment is appropriate.

The reason comes down to anatomy. ChondroFiller is a collagen scaffold that is placed directly at the load-bearing cartilage surfaces on the bone ends — the areas most exposed to focal wear and damage. Arthrosamid, by contrast, integrates into the synovial lining, the soft tissue layer that lines the joint capsule, where it provides durable mechanical cushioning. One targets the cartilage surface; the other works through the joint's inner lining. These are distinct structures, and a product designed for one cannot substitute for the other.

Clinical selection follows from that distinction. A focal, contained cartilage defect typically points toward ChondroFiller. Diffuse symptomatic osteoarthritis affecting the synovial environment typically points toward Arthrosamid. Where both pathologies are present on the same scan, a dual-injection protocol can deliver both in a single outpatient appointment — each product addressing a separate anatomical target through a different mechanism.

Both treatments are administered as ultrasound-guided injections in a clinic setting, not as surgical procedures. The sections below explain what each injection does, what the evidence shows, and how a specialist assessment — anchored to imaging — determines which pathway, or combination of pathways, is appropriate for a given patient.

How ChondroFiller repairs focal cartilage defects

At an outpatient appointment, ChondroFiller is placed into the damaged area of cartilage under ultrasound guidance — no theatre admission, no general anaesthetic, and no incisions. The product itself is a Class III CE-marked, acellular Type I collagen hydrogel scaffold manufactured by Meidrix Biomedicals in Germany. Once injected, it self-gels within three to five minutes at body temperature, conforming to the contours of the defect.

From that point, the scaffold functions as a chemotactic matrix. Rather than introducing laboratory-grown cells, it recruits the patient's own progenitor cells — drawn from the surrounding synovium and subchondral bone — to colonise the collagen framework and support endogenous repair. This process of acellular matrix-induced chondrogenesis unfolds gradually: the repair window is typically six to twelve months, and patients should not expect immediate relief in the way they might from a corticosteroid injection.

Because ChondroFiller is single-stage and acellular, it does not require the two-appointment pathway associated with cell-based alternatives such as Spherox, which involve harvesting and laboratory processing of a patient's own cells before a second procedure. Everything happens in one clinic visit.

Patient selection is specific. ChondroFiller is suited to focal, well-demarcated cartilage defects — grades III to IV chondral lesions, osteochondral defects, or damage following meniscal injury — in a joint with stable mechanics. Untreated ligamentous instability or significant malalignment are contraindications; the scaffold needs a mechanically sound environment to function effectively. Published data, including Demmer et al. (2025, PMC), report promising functional improvements in appropriately selected patients, with a headline figure of 70–85% meaningful symptom relief across knee and other joint applications at three to five years.

How Arthrosamid cushions the arthritic joint

Unlike ChondroFiller, Arthrosamid does not aim to repair or regenerate tissue. Its composition — 2.5% cross-linked polyacrylamide and 97.5% water — is engineered for mechanical cushioning rather than biological remodelling. Once injected into the synovial space under image guidance, the hydrogel integrates permanently into the synovial lining. It is not absorbed or broken down over time, which distinguishes it clearly from both corticosteroid injections and hyaluronic acid viscosupplementation.

The practical implications of that permanent integration are worth understanding. Patients are not receiving a temporary top-up: a single injection may provide sustained cushioning, with published studies reporting meaningful symptom relief lasting around five years, and re-injection remaining an option thereafter. Pain reduction tends to become apparent from approximately week four — faster than the tissue-remodelling timeline associated with scaffold-based options. In patients under 70, approximately 80% reported a positive response, according to available trial data. A 2022 paper by Maulana, Cole and Lee also reported reduction in patellofemoral bone marrow lesions following a single injection, suggesting a mechanical unloading effect that may extend beyond joint lubrication alone.

Arthrosamid received European regulatory approval in 2021 for symptomatic knee osteoarthritis and is backed by more than two decades of polyacrylamide hydrogel research. It is best suited to patients with diffuse synovial OA — particularly where conventional options such as hyaluronic acid injections have not provided lasting relief — and requires stable joint alignment. The evidence base, while promising, currently rests on open-label studies and smaller trials such as Bliddal et al. (2024) rather than large randomised controlled trials, and published outcomes should be read with that in mind.

What the current evidence shows for both

Placing both products on the same evidentiary footing reveals a consistent picture on safety as well as efficacy. For ChondroFiller, the published complaint rate stands at approximately 0.06% — a figure that reflects the acellular nature of the scaffold and its established tolerability across knee, hip, and small-joint applications. Arthrosamid's safety profile rests on a different foundation: polyacrylamide hydrogel has been studied in soft-tissue and musculoskeletal contexts for more than twenty years, and that research history supports the product's non-biodegradable integration without the tissue-reaction concerns that might accompany a shorter track record.

Neither product is yet supported by large, multi-centre phase III randomised controlled trials — the evidence for both currently rests on open-label studies and smaller clinical series, including Demmer et al. (2025, PMC) and Bliddal et al. (2024). That is an honest ceiling to state plainly, and it is shared equally. What the available data do show, consistently across both products, is a low adverse-event burden and durable symptom benefit in appropriately selected patients.

The practical implication is that the evidence is sufficient to inform a specialist consultation — not sufficient to allow self-selection between treatments. Which product is relevant, at what dose, and in which sequence depends on the MRI finding: that determination belongs with a clinician, not a published trial table.

Cost, access, and what the assessment involves

Both ChondroFiller and Arthrosamid are self-funded private treatments — neither is available on the NHS, and neither currently holds FDA approval for use in the United States.

UK guide costs are approximately £3,000–£8,000 for ChondroFiller, depending on the clinical requirements of the case, and approximately £3,000 for Arthrosamid. Quoted prices at many clinics include consultation, imaging, the product, the injection itself, and aftercare follow-up — but guide costs vary between providers and should always be confirmed with the treating specialist before proceeding.

The assessment pathway follows a clear logic. An MRI of the affected joint is the essential first step: the scan reveals whether the primary problem is a focal cartilage defect, diffuse arthritic change at the synovial lining, or a combination of both. That finding is what determines which product is appropriate — or whether a dual-injection approach in a single appointment makes clinical sense. Symptoms alone cannot answer that question reliably.

Eligibility criteria — covering joint stability, alignment, and the extent of any underlying structural damage — will be reviewed during specialist assessment. If any criteria are unmet, the clinician will identify them and discuss what should be addressed first. Specialist assessment, rather than self-referral to a specific product, is the right starting point for any patient considering either option.

Finding the right specialist for your situation

The MRI scan — not a product name, a price point, or a symptom checklist — is what ultimately determines which of these injections is relevant for a given knee. That principle is the practical takeaway from everything the preceding sections cover: the anatomical distinction between a focal cartilage defect and diffuse synovial change is the axis the decision turns on, and reading that distinction accurately is a specialist's job.

Three questions are worth raising at any assessment appointment:

• What does my MRI show — a focal defect, diffuse synovial change, or both?
• Am I a clinical candidate for one of these injections, or for a combined approach?
• What is a realistic outcome timeline for my specific situation?

Search MSK lists clinicians across the UK who carry out ChondroFiller and Arthrosamid assessments. Filtering by region and specialty is the most straightforward way to find someone whose practice covers the pathway relevant to your imaging.