Why candidacy depends on which ChondroFiller pathway you mean

Two distinct ChondroFiller® pathways are available at Lincolnshire Hip, and which one applies to you shapes every candidacy question that follows.

The first is ChondroFiller® Liquid Cartilage™ — an injectable collagen scaffold placed under ultrasound guidance to target a focal articular cartilage defect in the hip. Because it is designed to recruit the body's own repair cells into a specific lesion, it carries structural criteria around defect size, surrounding cartilage quality, and joint condition. The exclusions this guide covers all relate to this scaffold pathway.

The second is a ChondroFiller® collagen injection — a broader, top-down approach with no defect-size ceiling and no upper age limit, appropriate across a wider range of cartilage wear including higher-grade osteoarthritis. Being unsuitable for the scaffold route does not automatically close this door.

Both are outpatient, image-guided injection treatments. Neither involves surgery. The sections that follow explain specifically who falls outside the Liquid Cartilage™ scaffold candidacy window — and what the alternatives may be.

Advanced or diffuse hip OA that has passed the point of focal repair

Bone-on-bone contact, or what imaging reports describe as Kellgren-Lawrence Grade IV hip osteoarthritis, is the most common reason patients are declined for the Liquid Cartilage™ scaffold route. The mechanism explains why: the scaffold promotes endogenous repair by recruiting the body's own progenitor cells into a focal lesion — but that process depends on viable, reasonably preserved cartilage tissue at the defect margins to anchor and contain the collagen gel. When diffuse wear has consumed those borders across the entire hip joint surface, there is simply no structural environment left to support scaffold integration. The regenerative signal the acellular matrix is designed to trigger cannot work in a field where nothing salvageable remains.

Avascular necrosis (AVN) of the femoral head presents a related but distinct exclusion. Here the structural problem lies beneath the cartilage: compromised subchondral bone that can no longer supply the mesenchymal progenitor cells the scaffold depends on for acellular matrix-induced chondrogenesis. Without that cellular engine, the biological case for the Liquid Cartilage™ route does not hold.

Neither of these conditions necessarily closes every ChondroFiller® door. Patients with KL Grade III–IV hip OA who are excluded from the scaffold pathway may still qualify for the ChondroFiller® collagen injection, which acts as a top-down cushioning layer rather than attempting structural regeneration from within a focal defect. Where both ChondroFiller® forms are unsuitable, Arthrosamid — a long-lasting polyacrylamide hydrogel available at Lincolnshire Hip — provides an alternative route for symptom management in advanced hip OA.

Uncorrected bony deformity and the hip-specific mechanical gate

Achieving a durable repair requires more than filling a cartilage defect — it requires a mechanical environment that will not immediately destroy what forms there. That principle shapes the most important hip-specific candidacy gate of all: uncorrected femoroacetabular impingement (FAI).

In FAI, abnormal bony contact between the femoral head and the acetabular rim — whether from a cam lesion on the femoral neck, a pincer-type rim overhang, or both — generates repetitive cartilage abrasion. If that morphology remains uncorrected, any scaffold-supported repair tissue faces precisely the same mechanical insult that caused the original damage. ChondroFiller® Liquid Cartilage™ addresses the lesion; it cannot address the shape. Placing the scaffold without first resolving the impingement is unlikely to produce a lasting result, making uncorrected FAI an exclusion for the scaffold pathway as it stands.

Hip dysplasia — where a shallow or poorly oriented acetabulum distributes load unevenly across the joint surface — creates the same problem through a different anatomical mechanism. Significant leg-length discrepancy or ligament instability producing abnormal loading across the hip carry the same core principle: the mechanical environment must be stable before a regenerative scaffold has any prospect of surviving.

Crucially, none of these are necessarily permanent exclusions. Correction of the underlying deformity may open the scaffold pathway in appropriate cases. Prof Paul Y.F. Lee's hip-preservation assessment is structured around this sequencing — establishing first whether a correctable mechanical problem is present, and whether addressing it is realistic for a given patient, before any scaffold decision is made.

MRI and a clinical hip review are the tools needed to distinguish a correctable problem from irreversible structural deterioration.

Defect size, containment, and surrounding cartilage quality

Size and structural geometry place a further boundary around the scaffold pathway that is independent of arthritis grade or joint alignment.

The Liquid Cartilage™ scaffold is designed for isolated focal defects up to approximately 6 cm² — roughly the area of a fifty-pence coin. Defects substantially beyond that size exceed the range for which the treatment is supported. Equally important is containment: the scaffold relies on a firm rim of healthy surrounding cartilage to hold the collagen gel in position while repair progresses. Where the cartilage bordering the defect is itself degraded or absent, that anchoring rim does not exist, and the scaffold has insufficient purchase. A defect with ragged, compromised edges is a different clinical problem from one with sharp, intact margins — even if the measured area is similar.

Multifocal damage — where cartilage loss is scattered across several surfaces of the hip joint rather than concentrated in one discrete lesion — raises the same difficulty. A single scaffold treatment cannot adequately address multiple separate sites, and the clinical rationale for attempting it weakens accordingly.

None of this can be assessed reliably from symptoms alone. MRI showing the exact size, depth, and surrounding cartilage quality of a hip lesion is the essential starting point; without current imaging, candidacy cannot be meaningfully established in either direction.

Absolute contraindications that apply regardless of defect size

Three further exclusions sit outside the defect-size and alignment considerations covered earlier. They are mechanism-driven: no change in cartilage imaging, defect profile, or joint morphology will alter them.

Active hip infection is an absolute contraindication to any injectable scaffold device, including both ChondroFiller® pathways. Introducing a collagen matrix into an infected joint risks seeding the implant and could precipitate septic arthritis. The hip must be confirmed infection-free before any ChondroFiller® treatment is considered.

Confirmed allergy to murine proteins is an absolute contraindication to both forms. ChondroFiller® is derived from mouse (murine) Type I collagen — a detail unfamiliar to most patients. Anyone with a documented allergic response to mouse-derived material cannot safely receive the scaffold or the injection, regardless of how suitable the hip appears on imaging.

Substantially impaired healing biology acts as a relative contraindication for the Liquid Cartilage™ scaffold arm specifically. The scaffold mechanism depends on the body's own progenitor cells migrating into the collagen matrix and maturing into repair tissue. Active inflammatory arthritis in flare, or systemic immunosuppression from medication or underlying disease, is likely to limit that cell recruitment response. This is a clinical weighting rather than an unconditional hard stop — the degree of impairment matters — and it is assessed case by case at consultation rather than applied as a blanket rule.

What the right next step looks like when the scaffold route is not suitable

Being declined for the Liquid Cartilage™ scaffold route does not necessarily close every ChondroFiller® door. The ChondroFiller® collagen injection pathway — delivered as an outpatient, ultrasound-guided intra-articular injection — carries broader eligibility criteria: there is no defect-size ceiling and no upper age limit. For patients with diffuse wear or a defect that sits outside the scaffold's structural requirements, this top-down cushioning approach may still offer meaningful symptom benefit without demanding the focal containment the scaffold pathway needs.

Where both ChondroFiller® pathways are unsuitable — typically in KL Grade III–IV diffuse hip osteoarthritis where symptom management rather than tissue repair is the realistic goal — Arthrosamid is available at Lincolnshire Hip. Arthrosamid is a polyacrylamide hydrogel: a permanent, non-regenerative cushion that works through a different mechanism from ChondroFiller® entirely. It is not a scaffold; it does not recruit the body's own cells. The two options serve distinct patient profiles, and the distinction matters when weighing expectations.

For patients in whom hip replacement is the clinically appropriate treatment — end-stage disease, failed conservative measures, significantly impaired function — injection therapies are not a substitute. Honest counselling at that point means discussing timing, not alternatives.

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