Microfracture

For two decades this was the default cartilage operation: arthroscopic, single-stage, roughly 30 minutes, cheap. It remains the benchmark control arm of nearly every cartilage repair trial — which is also how we know precisely where it falls short.

How it works — and the built-in catch

An awl perforates the subchondral bone plate at the base of the defect so marrow blood, carrying mesenchymal stromal cells, clots into the defect and matures into repair tissue. The catch is well established: that repair tissue is predominantly fibrocartilage — type I collagen, mechanically inferior to the type II collagen of native hyaline cartilage. That composition explains both the reliable early benefit and the later wear.

What the evidence shows

The originator's own series looks best: 72 patients under 45 followed an average of 11.3 years, with Lysholm scores rising from 59 to 89 and 80% rating themselves improved at 7 years. It is uncontrolled, best-case selection, from the technique's inventor.

The wider literature is more sobering. A systematic analysis of 28 studies and 3,122 patients found function reliably improved during the first 24 months, but durability beyond that was conflicting, with deterioration reported after 5 years — and only 5 of 28 studies followed patients that long. A prospective cohort of 85 patients showed the timeline directly: significant improvement to 18 months, then significant deterioration between 18 and 36 months in every location except the femoral condyles. A systematic review restricted to level I/II studies concluded the same way: good short-term results in young patients with small lesions, but failures and osteoarthritis at 5–10 years regardless of lesion size — the authors advise reserving microfracture for small defects in lower-demand patients.

The head-to-head record

As the comparator in randomized trials, microfracture mostly loses. It was inferior to MACI at 2 and 5 years in defects of 3 cm² and larger (the SUMMIT trial), and inferior to osteochondral autograft (OAT) in young athletes at 3 and 10 years — failure 38% versus 14% at 10 years.

One head-to-head cuts the other way and keeps the field honest: the Norwegian RCT found first-generation ACI no better than microfracture at 14–15 years, with roughly half of both arms showing radiographic early osteoarthritis. The durability problem is not unique to microfracture, and "newer" has not always meant "better."

Where it still fits

The best-documented niche is a femoral condyle defect under about 2 cm² in a younger, lower-demand patient. Recovery is slower than the quick surgery suggests: weeks of protected weight bearing and continuous passive motion, because the clot is mechanically fragile, with total recovery around 6–9 months.

One downstream cost deserves more attention than it gets: marrow perforation alters the subchondral bone (intralesional osteophytes, cysts), which can complicate later cartilage procedures. Some surgeons now skip microfracture entirely in patients who may be candidates for future MACI or allograft.

Questions for your surgeon

• Is my defect small enough (under ~2 cm²) and on a femoral condyle — the niche where the data are best?
• What happens when the fibrocartilage wears — what is the revision plan?
• Would doing microfracture now compromise a later MACI or allograft if I need one?
• Given my activity level, would OAT or MACI's better randomized durability justify the bigger procedure?

Safety

Perioperative risk is low — standard arthroscopy, no implant, no donor site, no cell culture. The main harms are downstream: subchondral bone change, repair-tissue failure, and possible compromise of revision procedures. Whether augmented marrow stimulation (scaffolds, BMAC) meaningfully outperforms plain microfracture, or just adds cost, remains an open question.