The short answer for most patients

For most people asking this question, the answer hinges on two things: the extent of cartilage damage visible on imaging, and whether the joint around it is mechanically sound.

ChondroFiller™ is an injectable collagen scaffold suited to adults who have measurable cartilage damage — whether a focused lesion or more diffuse wear — and who want to preserve the joint rather than replace it. There is no fixed upper age limit on the injection pathway; active people in their 60s and 70s are routinely assessed, and the treatment is used specifically as a joint-preservation step before replacement surgery becomes necessary.

Post-traumatic presentations tend to fit particularly well: chondral lesions, osteochondritis dissecans (OCD), and cartilage damage following a meniscal tear or ligament injury are all considered appropriate — provided the wider joint structure remains intact.

The one condition that applies in every case is joint stability and alignment. Untreated ligament laxity, significant malalignment, or a meniscal deficit driving the wear needs to be addressed first, because the scaffold cannot compensate for underlying mechanical problems.

Joint conditions and cartilage grades that fit

The formal CE-mark indication sets a specific clinical threshold: Outerbridge grade III or IV cartilage damage. In plain terms, grade III means the cartilage has worn through to partial thickness with fissuring or softening across a defined area; grade IV indicates full-thickness loss exposing the bone beneath. Surface roughness alone — grade I or early grade II change — does not meet the published criteria for the regeneration pathway.

Defect size matters too. Published criteria indicate the scaffold is appropriate for localised lesions up to 6 cm², which covers the majority of focal cartilage injuries seen in clinical practice. Very large or uncontained defects — broadly, those exceeding 2.5 cm in diameter — fall outside the indicated range for the surgical regeneration route, though imaging-led assessment determines the final classification.

The injection pathway extends clinical suitability assessments beyond the knee. Joints routinely evaluated include the hip, ankle, shoulder, elbow, wrist, and small joints of the hand and foot, reflecting the scaffold's acellular, injectable format rather than a purely knee-focused application.

On the question of focal versus diffuse wear: the two patterns are not automatically treated as separate eligibility categories under the injection pathway. A contained focal defect is the textbook presentation, but more diffuse cartilage wear may still be assessed — the determining factor is what pre-treatment MRI shows, not a blanket rule about pattern type.

When ChondroFiller™ is not appropriate

Several clinical situations place ChondroFiller™ outside safe or useful territory, and recognising them early saves patients from an unnecessary assessment appointment.

Absolute contraindications

Because the scaffold is composed of murine-derived Type I collagen, a known allergy to collagen or to rat protein is an absolute bar — there is no formulation adjustment that removes this risk. Active infection within the joint is equally prohibitive; introducing any scaffold into an infected space would risk spreading the infection further. Pregnancy and breastfeeding are also listed contraindications.

Systemic disease

Inflammatory joint conditions such as rheumatoid arthritis and other inflammatory arthritides alter the joint environment in ways that impair tissue repair, making scaffold integration unlikely to succeed. The same applies to metabolic arthropathies — including gout and pseudogout — which generate a chemically hostile intra-articular environment. Active malignancy and haematopoietic disorders are also contraindications, reflecting the biological demands that scaffold-led regeneration places on the body's repair processes.

Advanced joint degeneration

For meaningful repair to occur, the joint needs enough residual biological capacity to support new tissue formation. In advanced osteoarthritis — bone-on-bone wear, Tönnis grade greater than 2 in the hip, or multi-compartmental joint destruction — that capacity is substantially depleted. The scaffold cannot restore a joint environment that no longer exists. In these situations, a different pathway is likely to be more appropriate, and a specialist assessment can clarify which options remain open.

Structural issues that must be corrected first

A separate group of patients falls between clear suitability and outright exclusion: those whose joint has a correctable mechanical problem sitting alongside the cartilage damage. These structural factors are not permanent disqualifications — they are pre-conditions that need to be managed before or alongside treatment.

Leg alignment. If the leg carries a malalignment greater than 5°, the scaffold is placed under uneven load distribution that it cannot withstand. Abnormal force concentration in one compartment undermines the repair environment regardless of scaffold quality. Addressing the alignment problem first may restore candidacy.

Ligament instability. An unstable joint shifts and shears in ways that prevent the scaffold from integrating properly. Untreated ligament injury is therefore a reason to pause the ChondroFiller™ pathway, not necessarily to abandon it — once stability is restored, reassessment is appropriate.

Meniscal deficit. When significant meniscal tissue is absent or severely damaged and is actively driving cartilage wear, that underlying cause needs to be addressed. The scaffold fills a defect; it does not replace the load-sharing and lubrication functions of meniscal tissue.

Patellar malalignment and arthrofibrosis. Both are listed in published criteria as structural factors requiring assessment. Restricted joint motion or abnormal patella tracking affects the mechanical environment in which any repair must occur.

In practice, the question is whether the structural problem is correctable and whether correction would leave the joint in a state where scaffold-led repair becomes viable — a judgement reached through imaging-led clinical assessment.

How suitability is assessed before treatment

The assessment is more than a review of scan images. Before confirming candidacy, a specialist will typically gather a full joint and medical history — including previous treatments, current medications, known allergies, and any of the systemic conditions covered in the previous section. A physical examination follows: weight-bearing posture, range of movement, ligament stability, and gait may all be assessed to verify what the imaging shows and to identify any mechanical factors that could affect treatment planning.

MRI remains the non-negotiable starting point. No reputable specialist will proceed without reviewing a patient's imaging — the scan reveals defect size, location, containment, and the condition of surrounding bone and soft-tissue structures in a way that clinical examination alone cannot. Patients who have not had recent MRI should expect this to be arranged before any treatment decision is taken.

Where imaging and examination together confirm a focal defect in a mechanically sound joint, the treatment pathway is typically an ultrasound-guided outpatient injection. Presentations that are structurally more complex, or where the defect characteristics differ, may be directed toward a different clinical route with its own eligibility criteria.

Final suitability is determined at the end of that structured review — not before it.

Realistic expectations for suitable candidates

Published comparative data report approximately a 30-point improvement in IKDC scores at 12 months in suitable patients — a figure consistent across early clinical series and broadly comparable with outcomes reported for autologous cell implantation techniques. Complication rates in those series are reported as very low, and reoperation rates of around 3–8% compare favourably with some surgical alternatives, where figures have been reported considerably higher. That said, high-quality head-to-head randomised trial evidence against other treatments is currently limited, and individual outcomes depend on a range of factors: age, activity level, defect characteristics, the condition of the surrounding bone, and how promptly the damage is addressed.

ChondroFiller™ occupies a different mechanistic category from lubricant or filler-style injections. This is a regenerative scaffold approach, not symptom masking: the collagen matrix is intended to support the joint's own repair processes rather than cushion or lubricate. Patients are therefore better served approaching the treatment as a longer-term joint-preservation strategy, with improvement typically building over months rather than days.

Meeting the candidacy criteria improves the likelihood of a useful outcome but does not guarantee one — and not every patient will qualify. For those who do not, the assessment does not end at that point. Alternatives including PRP, hyaluronic acid viscosupplementation, Arthrosamid®, or surgical referral can each be considered depending on the full clinical picture, ensuring the consultation remains constructive regardless of the outcome.