What HTO actually does for your knee

Can an operation on the tibia actually stop a knee getting worse? For the right patient, the evidence now suggests it can — and the proof is structural, not just subjective.

High tibial osteotomy works by correcting varus (bow-legged) malalignment at the top of the shin bone. By cutting and carefully repositioning the tibia, the surgeon shifts the weight-bearing line away from the damaged medial (inner) compartment and on to the healthier lateral (outer) side. Less load through the worn cartilage means less ongoing damage — a mechanical change with measurable biological consequences.

The clearest evidence of that comes from a 2025 randomised controlled trial published in the Annals of Internal Medicine (n = 145 adults with varus alignment and symptomatic medial-compartment osteoarthritis). Over two years, medial cartilage thickness loss in the HTO group was just 2%, compared with 9% in controls receiving conservative management. That is a structural difference — the cartilage is measurably better preserved, not merely less painful. On the KOOS symptom score, the HTO group improved by an average of 24.95 points versus 9.06 points in controls — a between-group difference of nearly 16 points, which exceeds the clinically meaningful threshold.

HTO is not a cure, and it will not last indefinitely for every patient. It is best understood as a joint-preservation procedure: one that buys meaningful time, keeps the native knee intact, and holds the door open for further options — including total knee replacement if and when that becomes necessary later.

The patient profile that gets the best results

Three factors from a 20-year prospective cohort of 100 patients identify who is most likely to do well: age below 55, BMI below 30, and a WOMAC functional pain score above 45 — that last figure matters because it marks residual joint function rather than end-stage disability. Patients who met all three criteria achieved 100% survivorship at five years, declining to 62% at 20 years, with 97% of those who retained their native knee reporting satisfaction with surgery.

These cohort criteria are the most rigorously validated predictors available, but clinical practice works within a somewhat broader envelope. The wider consensus profile — typically age under 60, isolated medial-compartment osteoarthritis with confirmed varus alignment, an adequate range of motion, a physically active lifestyle, and a course of conservative management already tried — captures the practical limits consultants apply when the strict cohort thresholds are not all met. Think of the cohort criteria as the bull's-eye and the consensus profile as the target around it.

Even radiologically advanced disease is not an automatic disqualifier. A systematic review of 18 studies covering 1,296 knees found average 10-year survivorship of 74.6% in patients with Kellgren-Lawrence grade ≥3 changes, with outcomes meeting established clinical meaningfulness thresholds. Selection in this group is more contested, however, and warrants careful specialist assessment.

Activity demands often tip the balance in borderline cases. For patients in their forties or early fifties whose work or sport would be incompatible with an implant, the case for preserving the natural joint — even at the cost of a more demanding recovery — tends to strengthen. Objective gait and alignment analysis, which provides measurable data on how load is distributed across the joint, can support that decision-making before any surgical commitment is made.

Timing: the window that opens and closes

The window for HTO is real and finite. The procedure works best when osteoarthritis remains confined to the medial compartment — before bone-on-bone contact becomes universal across the joint and before the lateral side shows meaningful deterioration. Once disease spreads beyond that boundary, HTO moves from indicated to contraindicated, and arthroplasty becomes the primary surgical option remaining.

The sequence matters in both directions. HTO follows confirmed failure of conservative care — once those non-surgical measures have been genuinely exhausted — rather than preceding them. Equally, prolonged delay carries its own cost: a patient who drifts from unicompartmental into bicompartmental disease loses access to joint preservation entirely, not just temporarily but permanently.

The 2025 RCT provides clear structural evidence of benefit at two years, but randomised data beyond that point do not yet exist. Survivorship figures over longer horizons come from observational cohorts — the 20-year data and systematic reviews discussed earlier are meaningful for planning purposes, but the absence of long-term RCTs is a real gap in the evidence base. Patients mapping out a decade-long strategy should understand that distinction.

One specific group occupies genuinely contested territory: patients aged roughly 55 to 65 who remain highly active. The upper age-BMI boundary is not settled in the published literature, and decisions in this group rest on individualised consultant assessment rather than fixed cut-offs.

When HTO is not the right choice

Several presentations make HTO unlikely to help — and identifying them early redirects patients towards options better suited to their situation.

• Bicompartmental or tricompartmental OA — realignment offloads one compartment; if both sides are significantly involved, there is no healthy compartment left to bear the transferred load.
• Inflammatory arthritis (rheumatoid, psoriatic) — systemic disease continues to drive joint destruction regardless of mechanical correction. Realignment addresses load, not inflammation.
• BMI ≥30 — consistently associated with substantially worse survivorship across cohort evidence and clinical guidelines. The 20-year data discussed earlier make this threshold explicit.
• Severe stiffness — a pre-operative flexion arc below 90° predicts poor functional recovery.
• Significant lateral-compartment disease — as noted in the timing section, this moves the procedure from indicated to contraindicated.

Ligament instability has historically appeared on the same list, but the picture is more nuanced. In specific circumstances — where realignment reduces stress on a reconstructed ligament — it has become an expanding indication rather than a flat exclusion. This is a specialist-level decision, not a straightforward green light.

Patients who fall outside HTO criteria are not without options. Unicompartmental or total knee arthroplasty, cartilage restoration techniques, and biologic support may all remain viable pathways depending on the precise clinical picture.

What the procedure involves and its safety record

During the operation, the surgeon makes a precise cut through the upper tibia — just below the knee joint — and opens or closes the bone to correct the varus angle. The repositioned bone is fixed in place with angle-stable locking plates and screws, holding the correction while the tibia heals. Most patients stay one to two nights in hospital.

Modern technique has substantially improved precision. Biplanar osteotomy (cuts in two planes rather than one) increases rotational stability and accelerates bone healing. Patient-specific cutting guides, manufactured from pre-operative imaging, allow surgeons to achieve the planned correction more reliably than standard instrumentation — reducing the risk of the most common intraoperative problem, lateral hinge fracture.

The most comprehensive safety data come from a systematic review of 7,836 patients: intraoperative complications occurred in 5.5% of cases and postoperative complications in 6.9% — rates comparable to other elective orthopaedic procedures. The dominant issues were lateral hinge fracture (9.1% in medial-opening HTOs), superficial wound infection (2.2%), and nonunion (1.9%). Loss of correction and implant failure each occurred in under 1.5% of cases.

If HTO eventually reaches the end of its effective life, conversion to total knee replacement is technically feasible, with published outcomes broadly comparable to a primary replacement.

HTO alongside cartilage repair and other surgical options

Against unicompartmental knee arthroplasty (UKA), the comparison is genuinely balanced rather than one-sided. Pooled head-to-head data suggest UKA tends to deliver faster early pain relief and somewhat lower short-term complication rates. In younger cohorts, however, HTO and UKA reach comparable patient-reported outcomes — and HTO carries one advantage that arthroplasty cannot match: it leaves the native joint intact, with no implant to wear out or eventually revise. For patients in their 40s or early 50s who want to run, cycle, or return to physically demanding work, that distinction carries genuine clinical weight rather than merely philosophical appeal.

HTO's role is also expanding well beyond isolated varus correction. It is increasingly performed alongside cartilage restoration procedures — MACI, AMIC, or osteochondral grafting — where continued malalignment would otherwise load a repaired surface and accelerate its failure. The principle is straightforward: biological and implanted repairs need a mechanical environment capable of protecting them, and HTO can provide that environment.

Meniscal pathology follows the same logic. A systematic review found that performing medial meniscus root repair concurrently with HTO produces better objective outcomes than HTO alone, indicating that concomitant pathology is best addressed at the same sitting where possible. Combining HTO with ACL reconstruction is a further expanding indication: correcting varus reduces stress on the reconstructed ligament and may support graft longevity over time.

Current evidence therefore positions HTO less as a stand-alone delaying tactic and more as a platform procedure — one capable of anchoring a broader joint-preservation strategy when cartilage, meniscal, and ligamentous work all depend on a corrected mechanical axis to succeed.

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6. [6] Incidence of Complications and Revision Surgery After High Tibial Osteotomy: A Systematic Review. (2023). https://doi.org/10.1177/03635465221142868 https://doi.org/10.1177/03635465221142868
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8. [8] Patient‐specific cutting guides increase accuracy of medial opening wedge high tibial osteotomy procedure: A retrospective case‐control study. (2024). https://doi.org/10.1002/jeo2.12013 https://doi.org/10.1002/jeo2.12013
9. [9] HTO, UKA, and PFO for Medial-Compartment Knee Osteoarthritis: A Narrative Review of Comparative Mechanisms, Clinical Outcomes, and Decision-Making. (2025). https://doi.org/10.3390/jcm14217882 https://doi.org/10.3390/jcm14217882