Who mosaicplasty suits — and what active patients can realistically expect

For most active patients considering ankle mosaicplasty, the shaping question is not about the surgery itself — it is whether they will genuinely get back to sport afterwards. The honest answer is: most do, but the range in the published literature is wide, and two distinct outcomes matter. Across studies, headline return-to-sport rates span roughly 62% to 97%; the more clinically meaningful figure — returning to the same sport at the same intensity — sits lower, typically 50%–80%. Both numbers belong in any realistic conversation, because a patient who resumes running but can no longer play football competitively has experienced a real, if partial, limitation.

Mosaicplasty (also called osteochondral autograft transfer, or OATS) is best suited to talar osteochondral defects larger than approximately 1.5 cm², or to cases where an earlier microfracture procedure has failed. The strongest evidence sits in skeletally mature adults under roughly 40. Sport clearance typically takes 6–12 months — longer than after microfracture — though the trade-off is a more structurally durable repair. A proportion of high-impact athletes, particularly those in football and basketball, shift to lower-impact activities long-term due to the ankle's sensitivity under repetitive load: a clinically significant pattern that the literature tends to under-report.

The sections below set out what the evidence shows, what influences individual outcomes, and where the procedure's limits lie.

What mosaicplasty involves at the ankle

The procedure centres on a simple biological principle: replacing damaged cartilage and the bone beneath it with structurally intact plugs taken from the patient's own knee — typically the lateral trochlear groove or femoral condyle, which are relatively low-load sites and geometrically compatible with talar defect dimensions.

Each plug is a cylinder of cartilage bonded to its underlying bone, press-fitted directly into a prepared channel in the talar surface. Where a defect is large, several plugs are arranged side by side to cover the affected area — the arrangement that gives the technique its 'mosaic' name. Harvest and implantation happen within the same operation, which is a practical advantage over two-stage, cell-based alternatives such as MACI or ACI.

Because graft material is drawn from the knee, a secondary injury risk at the harvest site is an inherent part of the procedure — one that influences patient selection and post-operative monitoring, and that the evidence quantifies in some detail.

Rehabilitation follows a staged protocol: non-weight-bearing for the first three weeks, progressing to full weight-bearing by approximately week eight, with sport-specific loading introduced incrementally thereafter. Individual programmes vary with defect complexity, graft integration, and surgical findings.

Return-to-sport rates: what the data actually show

Three named studies put numbers behind the headline figures. Steman (2019), in a cohort of 47 surgical patients, recorded the highest return-to-sport rate reported in the literature: 97% (95% CI: 85%–99%), regardless of pre-injury or post-injury sport level. That figure is encouraging, though it almost certainly reflects careful patient selection and should be read alongside results from longer follow-up series.

Keszég (2022) tracked 24 mosaicplasty patients for more than a decade and found approximately 95% returned to sport at some point during follow-up — yet only 67% reached their exact pre-injury level. The gap of roughly 28 percentage points between those two figures is the sharpest quantification in the evidence base of why the two definitions cannot be collapsed into one. For a patient whose pre-injury life included competitive football or recreational running at a fixed standard, the 67% is the figure that carries most clinical weight.

Lopes (2023), a prospective study of 58 active patients, reported a return-to-sport rate of 70.6% with an average return delay of 4.3 months — lower than Steman's figure but consistent with the multi-study practical synthesis of 62%–84% for return to any sport, and 50%–80% at pre-injury intensity.

Taken together, the evidence supports a guarded but genuine optimism: most patients treated with ankle mosaicplasty will return to some form of sport, but a meaningful minority will not recover their pre-injury level or intensity. Mosaicplasty patients also reach sport clearance later than those treated with microfracture — a recognised trade-off that reflects the biology of osteochondral plug integration rather than a shortcoming of the technique itself.

Pain relief and functional improvement

Behind the clinical scoring lies a practical question most patients arrive with: will the ankle hurt less, and will it hold up for ordinary life?

The AOFAS (American Orthopaedic Foot and Ankle Society) scale is a validated 0–100 measure covering pain, function, and alignment — 100 representing normal ankle function, scores in the 40s and 50s describing significant daily limitation. Published data show postoperative AOFAS averages of 80.6–87.1 following mosaicplasty, up from pre-surgical baselines in the low 50s. In practical terms, that shift corresponds to moving from persistent pain on walking and difficulty managing stairs to an ankle capable of sustained daily activity and, for many patients, a return to recreational sport.

Pain scores follow a comparable trajectory. On a ten-point visual analogue scale, patients report an average reduction of approximately 4.2 points — a reduction large enough to be clinically meaningful rather than marginal.

The scale of supporting evidence is substantial. Bruns (2021) pooled 11 studies covering 500 ankles treated with osteochondral autograft transfer and found excellent or good results at a mean follow-up of 62.8 months — a timeline that extends well beyond the initial recovery period and suggests durability rather than short-term relief. The AOFAS society position statement summarises the broader literature as achieving good-to-excellent outcomes in 95% of patients, while Barrached (2024) confirmed significant pain and functional improvement at one year in mosaicplasty cases reviewed at that institution.

These gains do not occur uniformly across every patient, and individual results depend on the factors discussed elsewhere in this article — but the direction and size of the functional improvement are consistent across the evidence.

Donor-site morbidity: understanding the knee harvest risk

Every ankle mosaicplasty creates two surgical sites, not one. The graft is harvested from the patient's own knee — typically the lateral trochlear groove or femoral condyle — leaving a secondary defect that carries its own risk of symptoms.

The scale of that risk varies considerably between studies. Andrade's 2016 systematic review, covering 21 studies and 1,726 patients, found mean donor-site morbidity of 19.6% in knee-to-ankle procedures. The most common complaint was pain or instability during daily living or sport — reported in 44% of morbidity cases — followed by patellofemoral disturbances, stiffness, and persistent pain, each accounting for around 13%. Shimozono (2019) placed the estimate considerably lower, at 6.7%–10.8%. That gap does not indicate a data quality problem; it reflects genuine differences in how morbidity was defined and ascertained across studies — whether researchers relied on patient-reported questionnaires, clinical examination, or structured follow-up interviews.

One finding from the Andrade data is particularly useful for planning: there was no significant correlation between the size of the talar defect and the rate of donor-site morbidity. Requiring a larger graft does not appear to predict a higher risk of knee symptoms.

For active patients, the knee donor site warrants specific attention. Symptoms such as anterior knee pain or instability can interfere with training and sport participation independently of how the ankle itself is recovering — meaning both sites require monitoring during rehabilitation. This is a recognised trade-off, and it warrants direct discussion as part of any pre-operative planning conversation rather than a reason to dismiss mosaicplasty as an option.

Factors that predict the best outcomes — and when to consider alternatives

Two factors emerge consistently from the research as the strongest predictors of returning to the same pre-injury sport level: younger age and a smaller defect. Patients under 25 with lesions below 2 cm² tend to produce the most reliable results, and Emre (2013) identified age, lesion size, localisation, and any concurrent surgical interventions as the principal determinants of final outcome.

Migliorini's 2023 systematic review — covering 184 articles and 8,905 procedures — adds useful nuance. Older age was independently linked to lower postoperative function scores, and higher body mass index was independently associated with graft overgrowth, a complication in which the transplanted plug rises above the surrounding cartilage surface. More surprisingly, lesion size and symptom duration did not show an independent association with outcome once other variables were accounted for. That finding suggests the widely cited size threshold may reflect how surgeons select candidates as much as any direct biological effect of defect dimensions.

Clinical risk factors that warrant concurrent management include ankle instability, subchondral cysts, and pre-existing osteoarthritis. Each can impair graft integration or accelerate wear at the repair margins, and addressing them alongside — rather than after — the cartilage procedure is generally preferable.

For defects above approximately 4 cm², or where a prior mosaicplasty has failed with the underlying bone still intact, alternatives such as fresh osteochondral allograft (OCA) or cell-based procedures like ACI and MACI are typically better suited to the defect size. Crucially, no high-quality randomised controlled trial has yet compared these options head-to-head specifically in active or athletic populations — a genuine evidence gap that makes individual clinical assessment particularly important rather than a straightforward protocol choice.

The practical upshot is that outcomes are most predictable when patient selection, concurrent joint conditions, and donor-site risk are all weighed before committing to surgery. Patients can arrange a consultation at MSK Doctors' Sleaford or Grantham clinics without a GP referral, directly at mskdoctors.com.