Who cartilage repair actually works for

Cartilage repair is not a universal solution for joint pain — and being clear about that upfront is the most useful thing this article can do. The patients most likely to benefit are younger adults who have a single, focal cartilage defect with healthy tissue surrounding it and a structurally sound underlying bone. That profile describes someone whose joint is, in most respects, intact — damage is localised rather than widespread, and the biological environment needed for repair to succeed is still in place.

Four variables drive the clinical decision more than any others: age, activity level, lesion grade, and lesion size. Younger, active patients tend to produce better biological responses and tolerate the rehabilitation that follows repair procedures. Lesion grade, assessed using the ICRS classification, reflects how deeply the damage runs — Grade 2 lesions involve less than half the cartilage depth; Grade 3 extend beyond the halfway point; Grade 4 penetrate through to the subchondral bone. Lesion size then helps determine which technique is appropriate, a question covered in later sections.

Before any repair plan is finalised, concomitant pathology must be identified and accounted for. Cartilage injuries frequently accompany meniscal tears, ligament instability, or malalignment, and evidence supports addressing all of these at the same time rather than sequentially — leaving them untreated undermines the repair and increases the risk of recurrence.

The most important boundary to understand early is this: cartilage repair targets symptomatic, focal defects in an otherwise healthy joint. Patients with diffuse or advanced osteoarthritis — where cartilage loss is widespread across the joint surface — are generally outside the scope of repair or restoration surgery. For those patients, joint preservation or replacement pathways are more appropriate. Recognising which side of that boundary a lesion falls on is the first gate in any serious treatment discussion.

How lesion grade and size shape the decision

Two numbers anchor most clinical conversations about cartilage repair: the ICRS grade of the lesion and its surface area in square centimetres. Together they narrow the field of viable techniques more reliably than any other pair of variables.

Grade reflects how far the damage extends through the cartilage — think of it as the depth of a pothole rather than its width. Grades 2 and 3, where the bone plate beneath remains intact, generally leave a broader range of options open. Grade 4 damage involves the subchondral bone, which shifts the choice towards osteochondral techniques — such as OATS or fresh osteochondral allograft — rather than surface-only approaches. Addressing bone loss alongside the cartilage surface becomes a technical requirement rather than an option.

Defect area is the second filter. Below roughly 2–4 cm², a wider range of techniques — including marrow stimulation and osteochondral autografting — remains clinically reasonable. Above 3 cm², the evidence shifts more clearly towards cell-based restoration. The SUMMIT trial, comparing MACI with microfracture in patients with symptomatic knee cartilage defects, found that those with larger defects reported meaningfully better KOOS pain and function scores with MACI at both two and five years — a concrete illustration of why size thresholds matter in technique selection.

Two secondary variables refine this picture further. Containment — whether the lesion is fully enclosed by intact cartilage walls — is a positive prognostic sign; uncontained defects are technically more demanding and may suit different approaches. Location within the joint also influences the decision: defects in the weight-bearing zone carry different mechanical stakes than those at non-load-bearing margins, and a specialist's recommendation will reflect that.

Preservation first — options before surgical repair

Surgical repair sits at the middle of the treatment pathway, not the beginning. For patients whose cartilage damage is early, or who are not yet suitable candidates for a repair procedure, load redistribution and non-surgical management are the appropriate starting point — and in some cases, they remain the right long-term strategy.

The most clinically significant preservation procedure is osteotomy — a bone realignment operation that shifts weight away from the damaged compartment of the joint. In plain terms, if a patient's leg alignment is directing excessive load through the injured area, correcting that alignment protects the cartilage from further deterioration. Osteotomy can be used independently, as a standalone measure to slow progression and delay the need for more involved surgery, or it can be planned alongside a cartilage repair procedure. The case for combining the two is compelling: malalignment left uncorrected at the time of repair substantially increases the risk of the procedure failing, which is why surgeons assess alignment as a prerequisite rather than an afterthought.

For patients who are not yet at the surgical threshold, or where malalignment is contributing to symptoms without severe cartilage loss, an unloader brace offers a non-invasive way to shift mechanical load away from the damaged side of the joint. It does not address the underlying damage, but it can reduce symptoms and slow progression during a period of conservative management.

Choosing preservation does not close the door on future repair. In fact, protecting the biological and structural conditions of the joint — the subchondral bone, the surrounding cartilage, and correct alignment — is precisely what keeps more advanced repair options viable if they become necessary later.

Repair and restoration techniques matched to your defect

The techniques available span from an ultrasound-guided outpatient injection to a full osteochondral transplant, with defect size as the primary sorting variable.

Microfracture in context

Historically the default for smaller defects, microfracture creates tiny channels in the subchondral bone to release marrow cells into the lesion. It generates fibrocartilage rather than true hyaline cartilage, and clinical benefit frequently declines within two to three years; evidence also points to collateral damage to the subchondral bone plate that can complicate subsequent repair. Specialist centres now reserve it for specific scenarios rather than applying it routinely.

AMIC — single-stage, small-to-moderate defects

Autologous matrix-induced chondrogenesis augments microfracture with a resorbable scaffold membrane, guiding the released marrow cells towards more organised repair tissue. Single-stage and requiring no second operation, it offers a practical step up from standard marrow stimulation without the complexity of cell-based procedures.

OATS / Mosaicplasty — typically 1–4 cm²

Osteochondral autograft transfer moves cylindrical plugs of full-thickness cartilage-and-bone from a low-load area of the patient's own joint into the defect. Single-stage and biologically matched, it carries ten-year follow-up evidence supporting durable outcomes in appropriately selected patients. The meaningful trade-off is donor-site morbidity: the harvest area can itself become symptomatic, particularly where a larger mosaic of plugs is required.

ChondroFiller injection — focal defects up to 3 cm² (extendable to 6 cm²)

ChondroFiller (also known as Liquid Cartilage™) is delivered as an ultrasound-guided outpatient injection, not a theatre-based procedure. The acellular collagen scaffold gels in place within the defect and recruits the patient's own progenitor cells to drive cartilage matrix formation. Because it is single-stage, cell-free, and leaves no donor site, it also keeps future treatment options open. It is not appropriate where advanced arthritis is already present in the joint.

MACI / ACI — 2–10 cm², two-stage

Both procedures involve an initial biopsy to harvest and culture the patient's own chondrocytes, then a second operation to re-implant them — in MACI, seeded onto a collagen membrane. Long-term evidence supports ACI in significantly delaying or avoiding joint replacement surgery, and the MACI format is the most evidence-supported route for larger defects where marrow stimulation underperforms.

Fresh osteochondral allograft (OCA) — large or post-traumatic defects

Where a lesion exceeds what autograft can fill, or significant bone loss accompanies the cartilage damage, donor osteochondral tissue provides a single-stage solution. Published long-term series report durable outcomes in younger patients with large or post-traumatic lesions, making OCA a well-established option when the patient's own graft volume is insufficient.

Getting the diagnosis right before any treatment decision

A normal X-ray is one of the most common sources of confusion in cartilage care. Hyaline cartilage leaves no shadow on a plain radiograph, so a significant defect may be entirely invisible on a scan that otherwise looks unremarkable.

MRI is the essential next step before any treatment decision. Standard sequences show the location, depth, and surface area of a lesion along with the condition of the subchondral bone beneath — directly relevant to technique selection. Advanced sequences add further resolution: T2 mapping, for instance, can detect whether remaining cartilage is losing water content before it visibly breaks down, giving the specialist an earlier signal than structural images alone provide.

Arthroscopy remains the definitive step when precise grading is needed or when non-invasive imaging leaves uncertainty. Its practical advantage is that diagnosis and treatment often happen in the same session — the surgeon confirms the defect, assesses surrounding tissue, and may complete a repair without requiring a separate second procedure.

Pre-treatment assessment should encompass the whole joint. Co-existing findings — bone oedema beneath the defect, adjacent tissue changes, or unexpected lesion geometry — can materially affect how a repair technique performs. Identifying these before planning begins, rather than during surgery, is what makes a thorough work-up a clinical requirement rather than a formality.

Choosing a specialist with the right expertise

Finding the right surgeon matters as much as choosing the right technique. Not every orthopaedic surgeon routinely performs the full spectrum of cartilage procedures: a specialist who offers microfracture may not have regular case volume in MACI, osteochondral allograft, or cell-based two-stage repair. For larger or more complex defects, seeking a centre with the specific procedural experience — rather than the nearest available surgeon — is a reasonable priority.

A few questions help gauge whether a surgeon's practice is well matched to your situation: Which cartilage techniques do you routinely perform, and at what volume? What defect size and ICRS grade suits each approach you offer? And how do you manage concomitant pathology — a meniscal tear, ligament laxity, or malalignment — when it accompanies the cartilage damage?

One further consideration: the evidence base for cartilage repair is substantially knee-focused. Ankle data exists, but published guidance for hip and shoulder defects is considerably thinner. Patients with non-knee lesions should look specifically for surgeons with documented experience in that joint, rather than assuming expertise transfers.

For most patients who are young, carry a focal lesion in otherwise healthy surrounding tissue, and arrive with a clear diagnosis, cartilage repair is real medicine with durably positive outcomes in published series. The decision is neither simple nor universal — but with the right grading, the right technique match, and a specialist whose case volume reflects genuine experience, it is navigable.

Search MSK lists cartilage repair specialists across the UK; filter by joint and treatment type to find a surgeon whose practice matches your specific defect.