Which option tends to fit which defect

The quickest way to sort these options is by joint, defect size and pattern of damage. A focal cartilage defect in a younger or middle-aged joint is a different problem from diffuse osteoarthritis, and the treatment logic changes with that distinction. In practical terms, smaller isolated defects often point towards graft-based or single-stage restoration, whereas larger symptomatic lesions more often need a more durable reconstructive option than older marrow-stimulation techniques.

• AMIC tends to fit selected ankle defects, especially talar lesions. In a 7-year ankle cohort, the average treated lesion was 1.8 cm², and outcomes improved by 2 years and stayed broadly stable through 5 to 7 years; published ankle series also show that instability and other mechanical problems often need dealing with at the same operation.
• MACI is more often considered for larger symptomatic knee defects. In the SUMMIT randomised trial, it outperformed microfracture at 2 years, and a 5-year follow-up for defects 3 cm² or larger suggested that advantage was maintained. Microfracture therefore has more of a historical role than a strong mid-term one.
• OATS uses the patient’s own cartilage and bone and, in review-level evidence, tends to suit smaller isolated lesions; OCA uses donor graft and is more often chosen for larger defects.
• Liquid Cartilage™ sits in the same restoration conversation as a scaffold-based option for suitable focal defects, while advanced diffuse OA usually falls outside the scope of restorative cartilage surgery.

Who tends to be a reasonable AMIC candidate

A reasonable ankle AMIC candidate usually has a localised, repairable lesion rather than cartilage loss across the whole joint. In the 2025 7-year ankle cohort, the typical defect was modest in footprint — about 1.8 cm² — and most were on the medial talar shoulder (46%) or lateral talar shoulder (31%), with smaller numbers involving both shoulders (10%) or the tibia (13%). That is the sort of anatomy most often represented in the published series, not end-stage ankle arthritis with broad wear.

The more straightforward profile in the literature is a patient having a first cartilage repair in an ankle without major unresolved risk factors. In the 2023 series of 130 AMIC procedures, previous cartilage surgery was linked to graft-related complications, and smoking increased the odds of revision for graft-related problems (OR 3.7). That does not make AMIC impossible in those settings, but it does make the decision more cautious and the journey potentially less smooth.

Mechanics matter as much as the surface defect. In a matched study with mean follow-up of 4.2 years, ankles needing lateral ligament stabilisation alongside AMIC had worse functional scores than isolated AMIC, even though MRI appearances were similar; when postoperative stability was good (CAIT >24), results came closer to the isolated group. In practice, that means AMIC candidacy is often about the whole ankle package — lesion, stability and prior treatment history — rather than the cartilage crater alone.

What AMIC recovery usually looks like

Ankle AMIC recovery is usually a slow-burn process, not a quick rebound. The evidence here does not support one universal week-6 or week-12 timetable, but it does show a clear overall pattern: in a 2025 prospective cohort, function and pain scores were meaningfully better by 2 years and stayed broadly stable through 5 and 7 years. In practical terms, recovery is more often judged by the gradual return of pain control, swelling settling, walking confidence and activity tolerance than by one fixed milestone chart.

A large part of the variation comes from what is done alongside the cartilage repair. In the 2023 series of 130 ankle AMIC procedures, 81.5% needed a malleolar osteotomy for access, and some patients also had associated ankle problems treated at the same sitting. Where lateral ligament stabilisation is added, the rehabilitation pathway may be more protective or simply different, and a matched study with mean follow-up of 4.2 years suggests that persistent instability can blunt functional recovery even when MRI appearances are similar.

Later surgery does not automatically mean the graft has failed. In that 2023 series, 54.6% underwent another procedure, but many were for hardware removal or other ankle pathology; only 28% of revision cases were linked to AMIC-related graft complications.

Why MACI usually holds up better than microfracture

For symptomatic knee defects, the clearest comparative signal is durability. In the randomised SUMMIT trial, MACI was clinically and statistically superior to microfracture at 2 years for KOOS pain and sports/recreation, with added gains in activities of daily living, quality of life and symptoms; adverse-event rates were similar. A 5-year follow-up of a prospective randomised trial then suggested that this advantage still held for symptomatic defects 3 cm² or larger, which is exactly where a short-term improvement can matter least if it does not last.

Part of that difference appears biological as well as clinical. Microfracture relies on marrow stimulation, and it has an important historical place, especially in simpler or smaller lesions, but the repair tissue it produces may be less durable over time. MACI is designed to create a more supportive repair environment, and a 48-month patellar/trochlear study showed why that matters: even when some patient-reported differences narrowed, only MACI produced a significant Tegner improvement, and MRI T2 mapping still favoured MACI at 24 and 48 months; microfracture repair tissue never reached native-cartilage-like values. That helps explain why many specialists now use microfracture more selectively rather than as a modern default for larger symptomatic knee defects.

How patients choose between OATS and a donor graft

Once osteochondral grafting is being discussed, size usually drives the decision. Review-level evidence suggests that OATS may fit smaller full-thickness, isolated knee lesions. That suits the logic of an autograft: the repair uses the patient’s own cartilage and bone, so there is no donor tissue to source, but the harvest site becomes part of the trade-off. For a small, contained defect, that may be a reasonable exchange; for a broader lesion, borrowing enough healthy tissue can become much less attractive.

A donor graft, usually called OCA or an osteochondral allograft, tends to enter the picture when the defect is larger or more complex. Published reviews point in that direction, and a 2025 systematic review found that OCA improved pain and function for larger defects and had relatively low failure rates in the settings studied. That still does not make it a universal winner. In practice, the choice often comes down to defect size, location, bone involvement, whether the lesion is isolated or more complex, and graft availability. The broad principle is straightforward: own tissue for smaller contained lesions; donor graft when the defect is too large for that to be sensible.

Where Liquid Cartilage may fit

Liquid Cartilage™ (ChondroFiller™) is generally discussed in the cartilage-restoration part of the pathway rather than in the same category as simple symptom-control procedures.

That is the most useful way to separate it from AMIC, MACI, OATS and OCA. Whether it suits a particular focal defect, and how it compares with scaffold-, cell-, or graft-based procedures, needs specialist assessment. By contrast, larger bone-loss lesions or advanced widespread wear usually lead into a different preservation or replacement discussion.

1. [1] Treatment options and outcomes for paediatric knee cartilage lesions: A systematic review. (2025). https://doi.org/10.1016/j.knee.2025.08.020 https://doi.org/10.1016/j.knee.2025.08.020