What HTO does and why it matters for younger, active patients

Between living with chronic knee pain and committing to a joint replacement, there is a third option that many patients — particularly those under 55 who want to stay active — are not aware of.

High tibial osteotomy (HTO) sits between those two points on the treatment pathway. When the knee is bowed slightly inward — a condition called varus alignment — the inner (medial) compartment bears a disproportionate share of body weight. In a healthy knee, load travels fairly evenly through the joint; in a varus knee, the arthritic medial side absorbs considerably more than its share, accelerating cartilage wear and deepening pain with every step.

HTO addresses this directly by reshaping the top of the tibia (the shin bone), nudging the mechanical axis — the line along which load travels through the leg — away from the damaged inner compartment and towards the healthier outer side. Offloading the arthritic area is how the procedure relieves pain.

There is a secondary biological effect worth noting. Relieving mechanical overload can create conditions in which fibrocartilage repair tissue gradually forms over damaged surfaces, even without a separate cartilage procedure. Evidence suggests this regenerative response occurs across a range of deformity severities and defect grades.

Because all native bone, cartilage, and ligaments are preserved, future options — including knee replacement if eventually needed — remain fully open. For patients with inner-compartment knee arthritis and varus malalignment, a specialist assessment is the appropriate starting point for exploring whether HTO is a suitable pathway.

Who is a good candidate — and who is not

Matching the right patient to HTO is where outcomes are made or lost — selection matters more than surgical technique alone.

The profile associated with the best results combines several factors: age typically under 55, BMI under 30–35, disease confined to the medial (inner) compartment, a functional range of motion, stable ligaments, and no underlying inflammatory arthritis such as rheumatoid disease. Patients who fit this picture closely are genuine candidates; those who do not may be better served by arthroplasty.

A 20-year prospective cohort of 100 patients illustrates what careful selection achieves. In the well-matched group (age under 55, BMI under 30, WOMAC pain score above 45), survivorship — defined as freedom from knee replacement — was 100% at five years and 62% at 20 years, with 97% of surviving patients reporting satisfaction. A separate systematic review of 1,296 knees found average 10-year survivorship of 74.6%, even in patients with radiologically advanced Kellgren–Lawrence Grade 3 disease — suggesting HTO remains a reasonable consideration beyond the earliest stages of osteoarthritis, though expectations should be calibrated to match the severity of disease at presentation.

Patients who assume they are too old for osteotomy may take some reassurance from a 2024 European consensus involving 94 orthopaedic surgeons across 24 countries, which found no reliable evidence to justify blanket exclusion on the basis of age or sex alone. Criteria-led selection — not age used as a proxy — is the appropriate framework. A 62-year-old with confined medial disease and good alignment potential may be a stronger candidate than a younger patient whose disease has spread beyond one compartment.

There are, however, clear situations where arthroplasty is the more appropriate route. Significant lateral compartment involvement, inflammatory arthritis, flexion contracture above 15°, BMI over 35, or marked ligamentous instability all weaken the case for HTO considerably. Establishing which compartments are affected and how extensively the cartilage is damaged is a necessary step before any decision is made — MRI assessment, including cartilage-specific imaging where indicated, can help clarify candidacy at the planning stage.

Medial opening wedge versus lateral closing wedge: the technique choice

The two HTO techniques achieve the same goal — shifting load away from the medial compartment — but work from opposite sides of the tibia.

Medial opening wedge HTO (MOWHTO) is akin to opening a book at its spine: a controlled cut is made on the medial (inner) side of the proximal tibia, a hinge of intact bone is preserved on the outer cortex, and the gap is opened to the precise correction angle before a metal plate locks everything in place. No bone is removed. This is now the dominant approach for most varus cases, partly because it allows stepwise, fine-grained adjustment without disturbing the fibula.

Lateral closing-wedge HTO takes the opposite approach — a small wedge of bone is removed from the outer tibia and the gap closed down. It remains the preferred choice where the kneecap already sits lower than average, since opening the medial side could worsen patellar position. Both techniques have established track records; the decision reflects individual anatomy and surgeon experience rather than a single universal rule.

Patient-specific cutting guides, now available for MOWHTO, have been shown to improve angular accuracy — relevant given that both overcorrection and undercorrection are associated with worse long-term outcomes.

Beyond correcting the left–right alignment, MOWHTO can simultaneously adjust the backward tilt of the tibial plateau, known as the posterior tibial slope. This extends the procedure's usefulness to patients with ACL insufficiency or meniscal transplant needs, not only those with straightforward varus arthritis.

The most common intraoperative technical complication of MOWHTO is lateral hinge fracture — a crack at the intact bone hinge — occurring in approximately 9.1% of medially based procedures across published series.

Combining HTO with cartilage repair: when and why it is done

Correcting varus alignment and repairing a focal cartilage defect in the same surgical episode follows a straightforward biological logic: a repair graft placed inside a malaligned knee still faces the adverse loading that caused the original damage. Correcting the mechanical axis simultaneously — or first — creates the conditions in which a cartilage repair has a realistic chance of surviving.

Isolated HTO can itself stimulate some fibrocartilage regeneration simply by relieving abnormal pressure on the medial compartment. When a discrete, full-thickness cartilage defect is also present, surgeons can add a cartilage repair procedure in the same operation. Matrix-augmented approaches such as AMIC and MACI, which aim to generate hyaline-like repair tissue rather than scar fibrocartilage, are commonly used in this combined setting; osteochondral autograft transfer (OATS) is an option for smaller contained defects, and osteochondral allograft for larger or post-traumatic lesions. Microfracture has been used historically — including in early combined series by Sterett and Steadman dating to 2004 — but its longer-term results are generally less durable than those of the matrix-based approaches.

The sharpest current evidence on whether combining procedures adds genuine value comes from a 2025 propensity-matched study. Additional clinical benefit appeared only in patients who had well-regenerated cartilage confirmed at second-look arthroscopy — their VAS, Lysholm, and KOOS scores were significantly better than those of matched isolated-HTO controls. Patients with poor cartilage regeneration gained nothing beyond what HTO alone provided.

Two practical thresholds inform the decision. A nationwide German cartilage registry analysis of 736 eligible patients (screened from 4,968) places the clinical breakpoint at 3° of varus for adding HTO to a cartilage repair case; a 2024 narrative review recommends osteotomy alongside any cartilage procedure when extra-articular deformity exceeds 5°.

Randomised trial data comparing isolated HTO with combined procedures remain sparse, and which cartilage repair modality performs best in the osteotomy environment has not been definitively established — so patient selection and technique choice continue to rest largely on cohort evidence and individual surgical judgement.

Risks, complications, and what the rates mean in practice

Pooled data from a systematic review of 71 studies covering 7,836 patients gives the clearest picture of HTO's safety profile. Roughly 5 in every 100 patients experience an intraoperative complication — a rate that, for a procedure involving deliberate bone cutting, is considered within an acceptable range for a joint-preserving operation.

The most common intraoperative event in medial open-wedge procedures is lateral hinge fracture, occurring in approximately 9 in every 100 medially based HTOs. Surgical experience and technique influence this figure; most hinge fractures, when recognised and managed at the time of surgery, heal without long-term consequence. After the operation, around 7 in 100 patients develop a complication — most frequently superficial wound infection (approximately 2 in 100) and nonunion, where the osteotomy gap is slow to consolidate (approximately 2 in 100). Both are generally manageable with standard wound care or prolonged protected weight-bearing respectively. Loss of correction over time — where the achieved alignment gradually shifts — is a recognised but less common finding, typically linked to early mechanical stress on the fixation.

Critically, none of these complications ordinarily closes off the patient's future treatment options. When conversion to total knee arthroplasty eventually becomes necessary, published data support good outcomes — meaning a complication after HTO rarely puts a patient in a worse position than if they had not had the procedure.

HTO versus knee replacement: how to decide which pathway fits

Three pathways compete for the same patient group: HTO, unicompartmental knee arthroplasty (UKA), and total knee arthroplasty (TKA). The decision is genuinely contested at the margins — which is worth stating plainly.

HTO's singular advantage is what it leaves behind: native anatomy intact, bone stock untouched, the knee's natural kinematics undisturbed. That matters most for patients who want to load their joint hard — running, manual work, sport — because no form of arthroplasty fully accommodates those demands without long-term trade-offs on implant longevity and activity restrictions.

TKA offers faster early mobilisation and more predictable short-term pain relief, but it removes the joint surfaces permanently and carries lifelong restrictions on high-impact activity. It is a definitive procedure, not a staging post. When an HTO eventually progresses to the point where conversion becomes necessary, published data indicate that subsequent TKA outcomes remain good — so a prior osteotomy does not close off that route, it defers it to a point when the patient's age, anatomy, and activity priorities may all be better matched to replacement.

The HTO-versus-UKA borderline is the harder call. UKA also spares the healthy compartment but replaces rather than unloads the diseased one; it generally suits patients with less severe varus deformity and typically requires an intact anterior cruciate ligament. When malalignment is substantial, or when ligament reconstruction is being considered alongside joint preservation, HTO carries the stronger mechanical argument. Neither the current evidence nor any published consensus fully resolves which approach wins in the overlap zone — the 2024 ESSKA consensus explicitly broadened HTO indications rather than narrowing them, underscoring that these remain judgement-based decisions.

A patient in that overlap — younger, active, medial disease, moderate varus — is exactly the case that rewards thorough individual assessment: imaging, alignment measurement, and a direct conversation about what the knee needs to do for the next decade. Lincolnshire Knee is part of the MSK Doctors group and accepts patients without referral — book an assessment at lincolnshireknee.co.uk.

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