Osteotomy (HTO) & realignment

Every other procedure in this section resurfaces cartilage. This one ignores the surface and fixes the physics. A cut in the proximal tibia — usually a medial opening wedge secured with a locking plate — shifts the weight-bearing axis away from the worn or repaired medial compartment onto healthier lateral cartilage. The rationale: repair tissue and remaining native cartilage both fail under focal overload; correct the axis, and everything downstream lasts longer. (Distal femoral osteotomy is the mirror-image operation for valgus knees.)

For a varus knee with a medial defect, alignment correction may matter more than which resurfacing procedure is chosen — the comparison between repairs is not always the first decision.

What the numbers show

• Long-term survival: in a series of 413 patients at mean 12 years, survival (avoiding knee replacement) was 95% at 5 years, 79% at 10, and 56% at 15; 85% were satisfied and 84% would repeat the surgery. Age under 50 and BMI under 25 predicted longer survival.
• Modern technique: a series of 125 open-wedge osteotomies with locking plates found 87.2% ten-year survival — 94.3% in the subgroup that had ACI alongside.
• Pooled conversion rates: a meta-analysis of 59 studies and 5,162 patients found conversion to total knee replacement of 4.5% before 5 years, 8.3% at 5–10 years, and 11.2% beyond 10 years, with 12.1% complications.
• Return to activity: across 19 studies and 1,189 patients, 87.2% returned to sport — 78.6% at an equal or higher level — with about 90% of returns inside a year.

One caution about the endpoint: "survival" means avoiding replacement, which can mask years of mediocre symptoms before conversion. And no RCT compares osteotomy against nonoperative care or against partial knee replacement in patients eligible for either.

Osteotomy plus cartilage repair: genuinely unresolved

The data disagree. A controlled series in mild varus (under 5°) found ACI-plus-HTO survival of 89.5% versus 58.3% for ACI alone at about 6 years — offloading protected the repair even at deformities many surgeons would ignore — and the HTO+ACI subgroup above did well at 10 years. But the 59-study meta-analysis found no significant survival benefit from adding cartilage repair procedures. The honest read: correcting alignment is well supported; whether to add a cartilage procedure on top is genuinely uncertain.

Who it helps

The classic candidate is the "too young for a replacement" knee: a younger, active patient with unicompartmental (usually medial) wear or a focal defect plus malalignment. Durable results are predicted by age under 50 and BMI under 25. Recovery is bone-healing-limited — 6–8 weeks of protected weight bearing, most people back to work and sport within a year — and plates are commonly removed later in a second, minor operation. A future knee replacement remains feasible but is technically harder, with higher complication rates than a primary replacement.

Questions for your surgeon

• Is my pain really unicompartmental, and how much correction are you planning?
• Should a cartilage repair be added to the osteotomy, given the conflicting evidence — or is realignment alone enough for my defect?
• What are your rates of nonunion and hardware removal?
• If I eventually need a knee replacement, how does this surgery change that operation?

Safety

This is a bigger surgery than the arthroscopic repairs: pooled complication rates run 5.8–12.1%, including nonunion (~1.7%), infection (~2–2.6%), hardware irritation, and rare nerve or vessel injury. Smokers and patients with BMI of 35 or higher fare worse.