Imaging before injection — the short answer

Before booking a ChondroFiller injection for your hip, a pre-treatment MRI is not a formality — it is the step that determines whether the treatment is appropriate at all. ChondroFiller is an injectable collagen scaffold engineered for a specific, anatomically defined focal cartilage defect. Without imaging, there is no confirmed target, and no basis for a safe treatment decision.

The London Cartilage Clinic's provider guidance names proceeding to injection without first reviewing a pre-treatment MRI as a clinical red flag — precisely because ChondroFiller cannot be aimed at a defect that has not been visualised and characterised. The Lincolnshire Hip suitability tool, reviewed by Professor Paul Lee, opens with a direct question about what the patient already knows about the state of their hip cartilage: a deliberate acknowledgement that meaningful candidacy assessment begins with imaging evidence, not symptoms alone.

In practice, one MRI drives three decisions simultaneously: whether a focal defect is present and of suitable grade, whether background osteoarthritis is mild enough to support a good outcome, and whether any underlying structural issue — such as femoroacetabular impingement — needs addressing alongside the injection. The rest of this article explains each of those decisions in detail.

Characterising the focal cartilage defect

The MRI essentially gives the clinician a map of the damage — its boundaries, depth, and position on the acetabular surface. ChondroFiller is designed for focal articular cartilage lesions, not for the generalised thinning that characterises widespread joint degeneration; distinguishing between the two is something a clinical examination cannot reliably do, but MRI can.

Defect area, measured in square centimetres, directly shapes the treatment plan. Broadly, lesions up to roughly 2–4 cm² and those beyond that threshold fall into different planning categories, affecting both whether ChondroFiller injection is the appropriate method and how much scaffold is required — typically one to three units scaled to defect size. In the Mazek et al. (2021) prospective cohort, all 26 patients had acetabular lesions larger than 2 cm²; defect volume was a core treatment-planning variable from the outset.

Depth matters as much as area. ICRS Grade 3 lesions — extending more than half the cartilage thickness — and Grade 4 lesions, where damage penetrates to subchondral bone, are the grades most relevant to ChondroFiller candidacy. Grade 4 with significant bone-on-bone loss generally redirects a patient towards joint replacement rather than scaffold injection.

Location introduces a further nuance. MRI sensitivity for cartilage damage on the posterior and inferior acetabular zones is lower than for the superolateral surface, even with high-resolution deep-learning protocols, which achieved only 42% overall cartilage lesion sensitivity in one 2025 study. Where clinical suspicion points to a harder-to-image zone, a specialist may request MR arthrography to characterise the surface more precisely before any injection decision is finalised.

Staging osteoarthritis before treatment

Alongside the focal defect itself, the MRI asks a second, equally important question: how much background wear does the hip joint as a whole carry? That background wear — osteoarthritis — is graded on the Tönnis scale from 0 (no signs) through to 3 (severe joint space narrowing with deformity). Grades 2 and 3 indicate that the cartilage loss has moved well beyond a single focal patch, and in that setting ChondroFiller lacks the conditions it needs to produce meaningful repair.

The Mazek et al. (2021) prospective cohort makes this concrete. The cohort's 81% good or excellent result rate at three to five years did not arise from the scaffold alone — it arose from strict pre-treatment imaging criteria that excluded patients with Tönnis grade 2–3 disease before a single injection was given. When the background OA is advanced, published outcomes are poor regardless of the quality of the scaffold, and the Mazek data establish that clearly.

The broader candidacy literature aligns with this picture. Kellgren-Lawrence grades I to III — a widely used plain-radiograph classification — correlate with ChondroFiller suitability, with preserved joint space serving as a supporting signal that adequate cartilage stock remains. However, plain X-ray captures only indirect signs of cartilage loss: joint space narrowing and subchondral sclerosis. MRI identifies early subchondral change and cartilage thickness loss at a stage when radiographs may still look acceptable, which means it can push a borderline patient definitively above or below the candidacy threshold before an irreversible treatment decision is made.

Being redirected away from ChondroFiller on the basis of Tönnis grade 2–3 findings is a protective outcome of the imaging review, not a failure of the process. It signals that the appropriate conversation has shifted — towards hip preservation surgery or, in more advanced cases, towards joint replacement.

Hip morphology — FAI, dysplasia, and why shape matters

Think of a cartilage lesion as a pothole and the hip's underlying shape as the road camber that keeps opening new ones. Repairing the pothole without addressing the camber leaves the conditions that caused the damage fully intact. This is why pre-treatment MRI assesses the entire joint architecture — not only the cartilage patch already present.

Femoroacetabular impingement is the predominant morphological finding in patients with acetabular cartilage defects eligible for ChondroFiller. It takes two broad forms: cam impingement, in which an aspherical femoral head jams against the acetabular rim during movement, and pincer impingement, in which the acetabulum over-covers the femoral head. MRI identifies both patterns, characterises labral involvement, and evaluates acetabular version — the rotational orientation of the socket — each of which bears on whether the underlying mechanics need concurrent attention before or alongside a scaffold injection.

The significance of this extends well beyond the initial injection decision. Treating a focal cartilage defect with ChondroFiller while leaving unaddressed impingement risks subjecting the regenerating repair tissue to the same abnormal contact forces that originally damaged the cartilage. Candidacy assessment is therefore a whole-joint evaluation: the suitability tool at lincolnshirehip.com reflects this logic by inviting patients to consider what they already know about their hip's overall condition, not simply the defect in isolation.

Where MRI identifies hip dysplasia — insufficient bony coverage of the femoral head — the picture shifts considerably. Dysplasia alters load distribution across a wider surface area and is associated with measurable cartilage quality deterioration on T2 mapping studies. Patients in this group are generally redirected towards a different management pathway, which may include acetabular re-orientation surgery, rather than focal scaffold injection. Identifying that distinction on imaging before any injection is planned is precisely the kind of decision that pre-treatment MRI is designed to support.

Which MRI sequences add value for hip cartilage

Standard 3T MRI is the baseline for hip cartilage candidacy assessment: it confirms defect presence, estimates area, grades OA severity, and evaluates joint morphology. For most patients, this single scan generates sufficient information for a candidacy decision.

Quantitative sequences: measuring cartilage health, not just structure

Two additional sequences — T2 mapping and T1rho — measure cartilage at a molecular level rather than simply recording its appearance. T2 mapping reflects water content and collagen arrangement within the matrix; early degeneration raises these values before surface damage becomes visible on conventional images. T1rho targets proteoglycan concentration, the component responsible for cartilage's compressive resilience. Both can detect deterioration that standard sequences would miss.

Their clinical value is not merely theoretical. In a hip intervention study, anterior lateral T1rho values showed a significant negative correlation (r = −0.45 to −0.64) with six-month patient-reported outcomes, suggesting that the biochemical state of the cartilage at the time of treatment influences how well the hip recovers. A clinician may request these sequences when standard MRI leaves uncertainty about remaining cartilage stock.

MR arthrography: a sharper view of the acetabular surface

Where the initial scan leaves the acetabular surface ambiguous — particularly in posterior and inferior zones where detection rates remain suboptimal even with high-resolution deep-learning protocols — MR arthrography can add definition. A small volume of gadolinium contrast is injected into the joint before scanning, distending the capsule and outlining the cartilage surface more sharply. This step is not routine, but it becomes relevant when standard imaging is indeterminate and a focal lesion is still suspected clinically. A normal standard MRI does not fully exclude early cartilage damage in the hip.

Whole-joint scoring and post-treatment monitoring

Pre-treatment scans are typically assessed using the SHOMRI (Scoring Hip Osteoarthritis with MRI) framework, which evaluates the whole joint systematically rather than the defect alone. After a ChondroFiller injection, MRI also serves as the primary monitoring tool: published clinical evaluation data show MOCART scores — a validated measure of repair-tissue fill and integration — progressing from approximately 65 at four weeks to 81–82 at twelve months, confirming scaffold maturation on imaging rather than inferring it from symptoms alone.

Getting a hip MRI in Lincolnshire — practical access

Open MRI at MSK House in Sleaford offers a practical starting point for Lincolnshire patients who need hip imaging before a ChondroFiller assessment. Available from £450, the scanner is optimised for hip conditions and is approved by the International Federation of Sports Medicine — and it is suitable for patients who find conventional bore scanning difficult because of claustrophobia. For those who already hold recent hip MRI images from another provider, bringing those results to a first appointment avoids a repeat scan.

No GP referral is required to access Lincolnshire Hip for hip assessment. Once imaging is in hand, Professor Paul Y. F. Lee reviews the findings as part of a full candidacy discussion — interpreting defect grade, OA stage, and joint morphology together, rather than treating any single measurement in isolation.

The sequence matters: imaging provides the objective evidence, clinical review interprets it, and injection planning follows only when both steps are complete. Patients who have not yet arranged a scan can do so through MSK House and bring the results straight to consultation.

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

1. [1] Pre-surgical hip cartilage evaluation using MRI T1rho mapping on periacetabular osteotomy (PAO) outcomes. (2025). https://doi.org/10.1093/jhps/hnaf069.216 https://doi.org/10.1093/jhps/hnaf069.216