What separates these two hip injections

The answer to 'which injection suits my hip?' depends not on brand preference but on what stage your joint has reached and which structure is damaged. These two treatments work through entirely different mechanisms and are designed for different points on the hip pain pathway.

ChondroFiller™ (Meidrix Biomedicals GmbH) is a biodegradable injectable Type I collagen scaffold — CE-marked as a Class III medical device — that gels inside the hip joint within approximately three to five minutes of injection. Its role is structural: the scaffold acts as a chemotactic matrix, drawing the patient's own progenitor cells from the surrounding synovium and subchondral bone in a process called acellular matrix-induced chondrogenesis. The target is a focal, contained Grade III or IV cartilage defect at a load-bearing bone surface, where healthy surrounding borders can still support a repair response. It is not suitable for widespread or late-stage hip osteoarthritis.

Arthrosamid® (Contura A/S) is a non-biodegradable polyacrylamide hydrogel — 97.5% water, 2.5% polymer — that works through synovial integration rather than tissue regeneration. Once injected, it becomes incorporated into the synovial lining of the joint capsule, providing durable mechanical cushioning and pain reduction. It does not repair cartilage structure; its role is palliation of diffuse joint degeneration where structural repair is no longer achievable.

At Lincolnshire Hip, both are delivered as ultrasound-guided outpatient injections. The comparison between them is therefore a clinical question — about disease stage and biological target — rather than a procedural one.

Which hip conditions each injection targets

If your MRI shows a localised patch of full-thickness cartilage loss — typically at the acetabular surface following femoroacetabular impingement (FAI) — and the surrounding cartilage remains largely intact, ChondroFiller may be a suitable option. The injectable collagen scaffold requires healthy cartilage borders to confine the gel and support the repair response it triggers; defects larger than approximately 6 cm² fall outside its indicated range. Younger, active patients with a contained Grade III or IV focal defect and no significant surrounding wear tend to be the strongest candidates.

ChondroFiller is not appropriate where cartilage loss is widespread or the joint has reached late-stage degeneration. Published cohort data (Mazek et al., 2021) found poor outcomes when ChondroFiller was used in hip patients with Tönnis grade 2–3 osteoarthritis — underscoring why disease staging matters before any treatment decision.

Arthrosamid suits a different point on the hip pain pathway: patients with more advanced, diffuse hip osteoarthritis where the priority is sustained symptom relief and improved function rather than structural tissue repair. Because the polyacrylamide hydrogel integrates into the synovial lining rather than filling a focal cartilage defect, it can provide meaningful cushioning even when widespread joint degeneration makes regenerative therapy unsuitable. It is worth noting plainly that Arthrosamid holds CE-mark approval specifically for knee osteoarthritis; any use in the hip is off-label and available privately only, through specialist clinics with appropriate experience in hip-specific image-guided delivery.

A 24-month PROMs cohort of 314 joints treated with polyacrylamide hydrogel — the active compound in Arthrosamid — found that older patients, those with a lower OA grade, and those without diabetes were more likely to achieve a clinically meaningful improvement. These factors are relevant to patient counselling when discussing Arthrosamid for hip pain.

Your specialist will confirm suitability for either injection based on disease stage, clinical history, and imaging — no single factor is sufficient on its own.

How long results from each injection tend to last

ChondroFiller's collagen scaffold resorbs over six to twenty-four months — but that window is where the clinical work happens. During resorption, the scaffold is actively recruiting the patient's own progenitor cells, which deposit repair tissue within the defect. What persists beyond scaffold degradation is not the injected material but the biological result it enabled. In well-selected patients, published MOCART scores of 70–87 and functional gains of approximately 30 IKDC points support benefit lasting one to five years or more. A 2025 ex vivo model confirmed that cell migration begins almost immediately, with DNA content within the scaffold more than doubling by day 14.

Arthrosamid operates on a different principle. The polyacrylamide hydrogel does not degrade; it remains permanently integrated into the synovial lining. Average symptom benefit from a single injection is quoted at approximately two to three years, and most patients require only one treatment. A prospective five-year extension study (n=49) reported sustained statistically significant improvements in WOMAC pain, stiffness, and physical function throughout follow-up, with no serious adverse device effects — providing the strongest published durability evidence for the active compound.

One important caveat applies to both treatments when considered for hip use: long-term outcome data for ChondroFiller injection in the hip remain limited, and the five-year PAAG study was conducted in knee joints. Hip-specific evidence for both injections draws on extrapolation from broader CE-mark data and case-series rather than dedicated hip trials. No head-to-head randomised controlled trial in the hip exists for either product. A specialist assessment at Lincolnshire Hip will include an honest discussion of these evidence limits alongside whatever is known about your individual joint.

When a combined approach is worth considering

Some patients present with both: a focal full-thickness cartilage defect at the acetabular surface and broader synovial inflammation driving pain from a different tissue compartment altogether. Because ChondroFiller addresses the bone-surface cartilage and Arthrosamid integrates into the synovial lining, both can be delivered in a single outpatient session when imaging and clinical assessment confirm that both components of pathology are present and accessible.

This is not a case of doubling up on similar treatments. The two products have distinct anatomical targets — one acting via acellular chondrogenesis at the cartilage surface, the other via synovial cushioning — so combining them addresses genuinely different sources of hip pain rather than reinforcing the same mechanism.

Combined use is not routine and is not appropriate for every patient. MRI assessment is essential to establish whether a contained focal defect sits alongside diffuse synovial involvement, and whether the hip's anatomy permits safe delivery of both injections in one visit. Where it is indicated, this approach may allow a more complete treatment response than either injection alone.

Procedure, cost, and getting assessed at Lincolnshire Hip

The hip's depth makes accurate needle placement considerably harder than in more superficial joints. A 2016 systematic review by Hoeber and colleagues found that landmark-guided hip injections achieved confirmed intra-articular placement in only 72% of cases (95% CI 56–85%), compared with 100% for image-guided techniques (95% CI 98–100%; p<0.0001). For a collagen scaffold or a permanent polyacrylamide hydrogel, a misplaced injection is at best ineffective — which is why ultrasound guidance is clinical standard for both ChondroFiller and Arthrosamid at Lincolnshire Hip, not an optional upgrade.

Once placed, ChondroFiller forms its scaffold in situ: no surgical incisions, no theatre admission, no general anaesthetic. Arthrosamid is delivered the same way — both are in-clinic treatments at an outpatient appointment.

Neither injection is NHS-funded for hip indications, and both require a private MRI-informed assessment to confirm suitability. As a guide, Arthrosamid is approximately £3,000; ChondroFiller ranges from £3,000 to £8,000 depending on defect size and the number of boxes required. Exact costs are confirmed at assessment.

Lincolnshire Hip, led by Professor Paul Y.F. Lee, offers assessment and ultrasound-guided injection at Sleaford and Grantham. Patients can be seen without a GP referral. An Open MRI assessment can be arranged beforehand to establish defect size, surrounding cartilage integrity, and overall disease stage — the information that makes the selection decision meaningful. Lincolnshire Hip is part of the MSK Doctors group.

Questions to bring to your hip consultation

Before any injection can be recommended, MRI is the essential first step — it confirms whether a defect is focal or diffuse, whether the surrounding cartilage borders remain intact, the overall OA grade, and synovial status. Without that information, the clinical decision between these two products cannot be made reliably.

When attending a hip consultation, the questions worth raising are:

• Is my cartilage defect focal and contained, or is the damage more widespread?
• Do I still have healthy surrounding cartilage that could support a repair scaffold?
• Am I a candidate for a repair approach, a palliative one — or both?
• Could a combined injection address more than one source of pain in the same appointment?

Some patients will find that neither injection is appropriate. Where hip OA has progressed beyond what either product can address, hip preservation surgery or hip replacement may be the more relevant pathway — and a specialist consultation is the right place to hear that clearly.

The question that cuts through most of the uncertainty is also the most direct: 'Does my imaging show a focal defect with healthy borders, or has the damage spread too far for a scaffold approach?' That single answer, confirmed on MRI, is what guides almost everything else in this decision.

Lincolnshire Hip is part of the MSK Doctors group and accepts patients without referral for hip assessment.

1. [1] A prospective, open-label, clinical investigation of a single intra-articular polyacrylamide hydrogel injection: a 5-year extension study. (2025). https://doi.org/10.1186/s13018-025-06526-0 https://doi.org/10.1186/s13018-025-06526-0
2. [2] Polyacrylamide hydrogel injections in knee osteoarthritis: A PROMs-based 24 month cohort study. (2025). https://doi.org/10.1016/j.jcot.2025.103136 https://doi.org/10.1016/j.jcot.2025.103136