What chondroplasty does — and what it cannot do

Chondroplasty will not fix damaged knee cartilage — and understanding that distinction is the most important thing a patient can know before considering it.

The procedure is arthroscopic: a surgeon inserts a small instrument through one or two incisions and works directly on the cartilage surface. The target is mechanical irritants — loose flaps, frayed edges, and fibrillated (roughened) patches of articular cartilage that catch against the opposing joint surface and generate pain, grinding (crepitus), swelling, or a locking sensation. Two technical approaches exist. Mechanical chondroplasty uses a motorised shaver to debride and smooth the damaged tissue. Thermal chondroplasty uses a radiofrequency probe to ablate and reshape the surface, though this approach carries a separate concern: the RF energy causes chondrocyte death in surrounding tissue and may penetrate as far as the subchondral bone, raising questions about long-term effects on the cartilage that remains.

Formal classification is unambiguous: chondroplasty sits in the palliative category of cartilage treatments, alongside debridement — distinct from repair procedures such as microfracture, and from restoration techniques such as autologous chondrocyte implantation or osteochondral grafting. Smoothing a damaged surface does not rebuild the proteoglycan-collagen matrix of true hyaline cartilage; no technique currently can. Symptom relief is achievable, but the cartilage defect itself remains.

Why cartilage cannot regrow after debridement

The limitation runs deeper than surface tidying. Articular cartilage is built from a dense, specialised matrix of proteoglycans and type II collagen — a tightly interlocked architecture that gives it its load-bearing and shock-absorbing properties. Once that structure is lost, debridement cannot reconstitute it. Chondroplasty removes the unstable, irritating fragments and leaves a cleaner surface, but an intrinsically incomplete one. As Richter et al. note in a widely cited review, no technique currently in clinical use can fully reproduce normal hyaline cartilage; chondroplasty makes no attempt to do so.

Radiofrequency (thermal) chondroplasty introduces an additional consideration. The RF energy that ablates the damaged tissue also causes chondrocyte death in the surrounding cartilage, and in some cases this effect may extend into the subchondral bone beneath. The long-term consequences for the cartilage that remains are not yet fully characterised — this is an open question in the evidence, not a proven harm in every patient — but it is a reason why the technique draws scrutiny when used near viable tissue.

For grade 3–4 defects on the Outerbridge scale, indicating deep or full-thickness damage, the ceiling becomes measurable. In a comparative study of 98 patients, BMAC combined with cartilage-derived matrix implantation produced significantly better outcomes than chondroplasty alone: VAS pain scores of 1.7 versus 4.4, and KOS ADL functional scores of 87% versus 55%. Defects at this depth need a procedure in a different category — one that attempts biological repair rather than surface management.

The defects it suits best

Defining the right clinical niche is where chondroplasty earns its place in the treatment pathway.

On the Outerbridge scale — the grading system most commonly used to describe articular cartilage damage — chondroplasty is best matched to grade 1 and grade 2 lesions. Grade 1 indicates surface softening or minor surface irregularity; grade 2 represents partial-thickness fissuring that does not yet reach the subchondral bone beneath. Both grades describe damage confined to the upper cartilage layers, and the mechanical irritants they generate — catching, locking, grinding, localised swelling — are exactly what debridement is designed to address. As a practical size threshold, lesions under approximately 2 cm² are considered within scope.

Two clinical presentations suit chondroplasty well: mild-to-moderate osteoarthritis generating primarily mechanical symptoms, and focal acute chondral injuries from trauma or sport where the damage is shallow and well-defined. Younger patients with early-stage damage, and those whose main complaint is mechanical rather than persistent background pain, tend to be the stronger candidates.

The procedure is not appropriate for all small lesions, however. A 2025 study found that performing chondroplasty for isolated medial patellar facet lesions during MPFL reconstruction produced no measurable clinical benefit compared with a matched group whose cartilage pathology was left untreated — suggesting incidental use during other procedures is not always warranted. The case for intervention needs to be made on the specific lesion, not assumed from its presence.

When a repair or restoration procedure is the better path

Defect size is the clearest organising principle when chondroplasty reaches its limit — the larger and deeper the damage, the further up the treatment hierarchy a patient is likely to travel.

For defects between approximately 1 and 2 cm², surgeons have historically turned to microfracture: perforating the subchondral bone to stimulate a marrow-derived repair response. It remains historically significant as the first widely adopted marrow-stimulation technique, but current evidence tempers its appeal — the fibrocartilage it produces begins to break down at around two to three years, and drilling the bone plate can compromise the foundation needed for any subsequent procedure. AMIC (autologous matrix-induced chondrogenesis) was developed partly in response to these limitations: it augments microfracture with a collagen scaffold that supports more durable fill, making it a single-stage bridge between marrow stimulation and cell-based repair.

Once defect size moves into the 2–10 cm² range, cell-based restoration becomes the relevant category. ACI (autologous chondrocyte implantation) and its matrix-supported successor MACI involve harvesting the patient's own chondrocytes, expanding them in a laboratory, and reimplanting them — a two-stage process that is resource-intensive but supported by long-term follow-up data showing results that outperform microfracture at medium and long-term horizons. For larger or posttraumatic defects where autograft is insufficient, osteochondral allograft (OCA) transplants donor tissue including the underlying bone layer.

Chondroplasty can function as a bridge within this hierarchy — relieving mechanical symptoms while a patient undergoes specialist assessment to determine whether a restorative procedure is indicated — but it does not substitute for these techniques when the defect depth or size calls for biological reconstruction. Richter et al. classify chondroplasty explicitly as palliation, a distinct category from repair or restoration, and the evidence at each tier reflects that boundary.

Realistic expectations: what the evidence says

The most detailed aggregate picture of radiofrequency chondroplasty comes from a 2023 systematic review of 10 studies covering 1,107 patients and 1,504 lesions: mean postoperative Lysholm scores of 83–91, IKDC scores of 49–90, a complication rate of 0–4% (most commonly osteonecrosis), and a reoperation rate of 0–4.5%. For a procedure positioned at the palliative end of the treatment hierarchy, that is a broadly favourable short-to-medium-term safety profile.

What those numbers represent matters as much as the numbers themselves. Lysholm and IKDC scores capture function and symptom burden — reduced catching, locking, and pain are the realistic primary outcomes. Cartilage restoration is not on offer; the tissue that was lost remains lost.

One worthwhile technical footnote on radiofrequency technique: bipolar RF devices produce a wider and deeper zone of chondrocyte death around the treated area than monopolar devices — a distinction relevant when a surgeon is selecting equipment, even if the long-term clinical significance across both device types remains unresolved.

The wider evidence base carries honest gaps. Long-term natural history data for chondroplasty as a standalone treatment are limited, and commentary on the ChAMP trial has noted that no randomised study has clearly demonstrated superiority of chondroplasty over observation for mild defects. Symptom improvement after the procedure cannot therefore be confidently attributed to debridement alone rather than to the natural fluctuation of early-stage disease.

Perhaps most important for any patient weighing this option: chondroplasty does not alter the progression of underlying cartilage loss. Symptoms may ease; the disease course continues.

Talking to a specialist and next steps

For most patients with mechanical knee symptoms — catching, locking, or localised pain from a focal chondral injury — the appropriate starting point is a structured specialist assessment. That means MRI to characterise the defect by grade, size, and location, combined with a review of the patient's age, activity demands, and symptom history. Together, those factors determine whether chondroplasty is a reasonable first step or whether the damage already warrants a repair or restoration procedure. The same grade 2 lesion looks quite different in a 35-year-old recreational runner and a 58-year-old with early periarticular changes — and the treatment conversation should reflect that.

Search MSK lists knee cartilage specialists across the UK; filter by region and specialty to find a clinician suited to the specific presentation.