How your scan is scored — and what a good result looks like

If your scan report mentions 'signal changes' or 'repair tissue heterogeneity', it can be hard to know whether that is reassuring or concerning. The answer depends on where those changes sit, how old they are — and whether they are being read against a consistent framework.

All published ChondroFiller injection studies use a scoring system called MOCART 2.0 (Magnetic Resonance Observation of Cartilage Repair Tissue), a structured 0–100 scale specifically designed for cartilage repair assessments. Rather than a simple pass or fail, it scores seven distinct MRI variables that together capture both the structural quality of the repair and the health of the tissue around it.

For practical purposes, those variables fall into two groups:

• Fill and integration — how completely the collagen scaffold has occupied the defect, whether the repair tissue is flush with the surrounding native cartilage, and how smoothly the two are merging at their shared border.
• Tissue health signals — the signal intensity of the repair tissue itself, any bony changes beneath the surface, the presence of bone marrow oedema, and whether subchondral cysts have formed.

A score above roughly 80 corresponds to greater than 80% defect fill and good peripheral integration. Across multiple European ChondroFiller injection studies, mean MOCART scores at one year ranged from 81.6 to 84.3 — a benchmark worth keeping in mind when a reviewing clinician translates your own scan into this framework, since most radiology reports will not include a raw MOCART figure.

The 4-week scan: what shows up this early

Receiving that first scan result four weeks after a ChondroFiller injection is, for most patients, the most nerve-wracking moment in the process. The numbers look lower than the benchmarks described in the previous section — and that is completely expected.

The Schneider 2016 randomised controlled trial, which used MOCART imaging at both the four-week and one-year mark, recorded a mean score of 65.3 at the early time-point. That figure is not a poor result; it is the normal baseline for a scaffold that has filled the defect and begun integrating with the surrounding cartilage, but has not yet started to mature. The four-week scan is essentially confirming two things: that the injectable collagen has occupied the defect, and that the repair tissue is beginning to merge at its edges with the native cartilage around it. It is not — and cannot be — a picture of finished cartilage.

There is a practical reason the repair looks incomplete this early. Biomechanical laboratory data (2024) confirm that ChondroFiller has initial mechanical instability before the scaffold stabilises within the defect. This is precisely why post-injection activity restriction is recommended: it is not arbitrary caution, but a response to the physics of early-stage repair tissue. Loading the joint too soon risks disturbing a scaffold that has not yet anchored firmly.

The four-week scan is a starting point, not a verdict.

Bone marrow edema and interface signals: what is normal in the first 18 months

Two phrases appear regularly in cartilage repair scan reports and reliably cause unnecessary alarm: 'bone marrow oedema' and 'incomplete integration at the repair border'. Both are expected findings in the months after a ChondroFiller injection — and understanding what they mean separately helps make the report readable rather than frightening.

Bone marrow oedema shows up as a bright patch on fluid-sensitive MRI sequences (typically STIR or proton-density fat-saturated images) in the bone directly beneath the repair site. This brightness reflects increased water content in the subchondral bone — a normal biological response to the repair process above it. It is expected to be present throughout the first twelve to eighteen months and does not indicate that something has gone wrong. The point at which its persistence becomes a reason for clinical review is beyond eighteen months; before that, its presence on a scan is neither surprising nor cause for concern.

Interface signal at the repair border — sometimes described as streaky hyperintensity between the repair tissue and the surrounding native cartilage — reflects incomplete bonding at that junction. On early scans this is a normal finding; the scaffold and native tissue are still consolidating. If the same signal persists on a scan taken at two years or later rather than resolving, that is the point at which a treating clinician needs to assess the integration.

These are named, monitored findings — not incidental problems. Knowing their normal timeframes means reading the scan report alongside them rather than around them.

How the scan changes from 4 weeks to 12 months and beyond

The signal changes that appear on successive scans tell a more detailed story than a single number. As repair tissue matures inside the ChondroFiller scaffold, its MRI signal intensity shifts progressively from bright (hyperintense) toward a shade that more closely matches the surrounding native cartilage — a visual marker of collagen fibres organising within the matrix. This is the biological process that drives the MOCART score improvements seen in the European clinical studies: early partial maturity gradually giving way to the 81–84 range by twelve months.

Where specialist imaging centres include T2 mapping, the picture becomes quantitative. This technique measures how water molecules move within the cartilage matrix, which reflects collagen organisation. The T2 index — repair tissue signal divided by the signal of adjacent normal cartilage — typically sits around 1.7 at six months and decreases toward 1.0 over the following twelve to eighteen months; a lower value reflects a more hyaline-like tissue structure. Not every scan report includes T2 mapping, but when it appears, a declining index is a reassuring sign of continued maturation rather than something requiring explanation.

These imaging changes correspond to genuine cellular activity rather than signal artefact. A 2025 ex vivo study confirmed a 2.4-fold increase in DNA content within ChondroFiller scaffolds by day 14, providing direct laboratory evidence that the scaffold is actively recruiting the patient's own cells — precisely the process that successive scans track over months.

Because the same collagen matrix and the same host-cell recruitment mechanism operate wherever the scaffold is placed, this maturation trajectory extends beyond the knee. A hip cohort study (2021, n=26) followed patients using MRI for three to five years and found 17 of 21 patients achieved good or excellent results. One meaningful moderator emerged from that data: patients with established Tönnis grade 2–3 osteoarthritis before treatment had poorer outcomes — which is why baseline OA severity is assessed before any ChondroFiller injection is planned.

When technique matters: what overfilling looks like on scan

The 2025 wrist cartilage study provides a clinically specific finding that goes beyond the scoring numbers covered earlier: fibrous tissue formation at the repair site on follow-up imaging occurred exclusively in defects that had been overfilled, while flush applications — where the scaffold was placed level with the surrounding cartilage surface — showed no such change.

Fibrous tissue carries a distinct signal character from maturing cartilage repair tissue. On standard MRI sequences it appears brighter and more homogeneous than the progressive signal normalisation described in the previous section, and it does not follow the same maturation trajectory toward native cartilage signal intensity.

The implication is straightforward: what the scan shows at follow-up is partly determined by how precisely the scaffold was placed at the time of injection. Volume control during placement — avoiding overfill — is a technical variable, not an anatomical one.

For patients whose scan report notes a fibrous signal at the repair site, overfill is a recognised and discussable cause. The appropriate question to raise with the treating clinician is whether fill level was a factor and what the monitoring or management plan should be in response.

Real-time ultrasound guidance during injection allows the clinician to visualise placement depth and fill volume as the scaffold is delivered — which is why image-guided placement, rather than freehand delivery, is standard practice for ChondroFiller injection.

Your scan schedule and what the results guide

Serial MRI rather than a single scan is what makes the monitoring programme genuinely useful. A scan taken at one year carries more meaning when it can be compared against the four-week baseline: the clinical team is asking whether defect fill is holding, whether the repair signal is continuing to mature, and whether any bone marrow oedema seen earlier has resolved on schedule.

Where the imaging shows incomplete fill or a signal that has not progressed as expected, a top-up ChondroFiller injection may be scheduled — re-introducing scaffold material to reinforce or extend what the first treatment established. This decision is made jointly with the scan findings and clinical outcome scores rather than on imaging alone.

Patients who want their existing scan reviewed, or who are considering whether ChondroFiller injection is appropriate for their cartilage defect, can book an assessment at the London Cartilage Clinic on Harley Street via londoncartilage.com.

One pattern worth noting before any scan appointment: patients with Tönnis grade 2–3 osteoarthritis established before treatment showed poorer MRI outcomes in the hip cohort data at three to five years. Where that degree of background joint change is already present, the maturation trajectory that successive scans track may differ from what earlier sections describe — and managing expectations around that distinction is part of what an informed review appointment covers.

1. [1] The MOCART (Magnetic Resonance Observation of Cartilage Repair Tissue) 2.0 Ankle Score. (2024). https://doi.org/10.1186/s13244-024-01696-7 https://doi.org/10.1186/s13244-024-01696-7
2. [2] Controlled, randomized multicenter study to compare compatibility and safety of ChondroFiller liquid with microfracturing of patients with focal cartilage defects of the knee joint. (2016). https://doi.org/10.5348/VNP05-2016-1-OA-1 https://doi.org/10.5348/VNP05-2016-1-OA-1
3. [3] Arthroscopic utilization of ChondroFiller gel for the treatment of hip articular cartilage defects: a cohort study with 12- to 60-month follow-up. (2021). https://doi.org/10.1093/jhps/hnab002 https://doi.org/10.1093/jhps/hnab002
4. [4] Cartilage reconstruction using Chondrofiller in intra-articular distal radius fractures. (2025). https://doi.org/10.1186/s42836-025-00333-y https://doi.org/10.1186/s42836-025-00333-y
5. [5] Influence of cartilage defects and a collagen gel on integrity of corresponding intact cartilage: a biomechanical in-vitro study. (2024). https://doi.org/10.1007/s00402-024-05530-z https://doi.org/10.1007/s00402-024-05530-z
6. [6] Time-Dependent Change in Cartilage Repair Tissue Evaluated by MRI up to 2 Years After Atelocollagen-Assisted ACI (CaTCh Study). (2022). https://doi.org/10.1177/19476035221109227 https://doi.org/10.1177/19476035221109227
7. [7] Chondral and Osteochondral Femoral Cartilage Lesions Treated with GelrinC: T2 Mapping at 24 Months. (2020). https://doi.org/10.1177/1947603520926702 https://doi.org/10.1177/1947603520926702
8. [8] Development of an Ex Vivo Osteochondral Biomimetic Platform for Mechanistic Investigation of Cartilage Regeneration. (2025). https://doi.org/10.3390/ijms262311759 https://doi.org/10.3390/ijms262311759