What the evidence actually shows

The question most patients ask is straightforward: will this surgery mean I never need a knee replacement? The honest answer is that it will not eliminate that possibility — but for most people, it can substantially defer it.

The clearest evidence comes from a prospective cohort study published in 2021 by Primeau and colleagues, which tracked 556 patients who underwent 643 medial opening-wedge high tibial osteotomy (HTO) procedures. At five years, only 5% had gone on to need a total knee replacement (TKR). By ten years, that figure had risen to 21% — which means 79% of treated knees remained replacement-free at the decade mark.

Put plainly, HTO is not a cure for osteoarthritis. The underlying condition continues, and for roughly one in five patients, TKR becomes necessary within ten years. What the surgery offers instead is a clinically meaningful delay — typically seven to ten years without replacement, and potentially ten to fifteen years when combined with cartilage restoration procedures. For an active person in their forties or early fifties facing an arthritic knee, that window can represent a significant portion of their most physically active years.

The goal, then, is to improve function and postpone replacement — not to make it unnecessary forever.

How realigning the tibia protects the joint

Medial osteoarthritis does not damage the knee evenly. In a varus — or bow-legged — knee, the mechanical axis of the limb runs too far toward the inside of the joint, meaning the medial compartment absorbs a disproportionate share of every step's load. That concentrated pressure accelerates wear on cartilage that is already compromised, creating a self-reinforcing cycle of degeneration.

HTO interrupts that cycle at its mechanical root. The surgeon makes a carefully planned cut across the upper tibia and opens a wedge of bone, tilting the tibia so that the weight-bearing axis shifts outward — away from the arthritic medial compartment and toward the healthier lateral compartment. Trevor Birmingham, the lead researcher behind the 2021 prospective cohort study, compared this to "a front-end alignment on a car to stop asymmetric tyre wear": the vehicle has not changed, but load is now distributed where the rubber can handle it.

Once the mechanical stress on the damaged side is reduced, two things follow. Pain diminishes because the most worn surfaces are no longer under the greatest load. And residual cartilage, no longer ground down at the same rate, can survive considerably longer than it otherwise would — creating conditions in which biological repair of the joint surface also becomes viable. The surgery works not by numbing the joint but by removing the mechanical driver of cartilage loss.

Who is a realistic candidate

Not everyone with a worn medial compartment will benefit equally from osteotomy — and the evidence is reasonably specific about who fares best.

The strongest candidates are typically active patients under around 60 years of age who have isolated medial-compartment osteoarthritis, a confirmed varus (bow-legged) deformity, and an intact lateral compartment and patellofemoral joint. A BMI under 30 is generally considered optimal; higher body weight places proportionally greater demand on the corrected alignment and is associated with a meaningfully higher rate of eventual conversion to TKR. Age below 55 is associated with the most durable outcomes — patients over 56 tend to show faster deterioration over time.

Radiographic OA severity at the time of surgery is the single strongest predictor of early failure: in the Primeau 2021 cohort, a higher grade of arthritis on imaging at the point of surgery carried an adjusted hazard ratio of 1.96 for conversion to TKR, roughly doubling the risk. Female sex (HR 1.67) and each additional decade of age (HR 1.50 per 10 years) also significantly raised conversion risk in the same dataset.

Where osteoarthritis is diffuse — affecting multiple compartments rather than predominantly the medial side — osteotomy alone is unlikely to provide adequate relief, and joint replacement becomes the more appropriate discussion.

Before any decision is made, pre-operative assessment including imaging is essential, and arthroscopy is typically performed to confirm the health of the lateral compartment, particularly when cartilage restoration is being considered alongside the osteotomy. Self-selection is not sufficient: a consultant assessment is required to weigh the full picture.

What surgery and recovery involve

The procedure itself is well-established and well-supported. Surgeons performing medial open-wedge HTO make a carefully planned cut across the upper tibia, open a measured wedge, and fix the corrected position using angle-stable locking plates — a method that has largely replaced older fixation techniques. A biplanar cut, dividing the tibia in two planes rather than one, is increasingly used because it improves stability at the correction site and creates better conditions for bone healing.

Under general anaesthetic — often combined with a spinal block for post-operative pain control — surgery typically takes around one to two hours. Most patients stay in hospital for one or two nights.

Recovery follows a predictable course. The osteotomy consolidates in approximately six weeks, during which weight-bearing is graduated carefully according to individual progress. Full rehabilitation, covering the return of strength, proprioception, and confidence under load, generally takes three to six months.

The functional gains for suitable patients are striking. Knee function scores on the Lysholm scale — a validated patient-reported measure — typically rise from the 40–65 range before surgery to 85–95 afterwards, roughly doubling. Around 90% of patients return to sport, including running, cycling, golf, and hiking.

Looking further ahead, joint survivorship without arthroplasty stands at 85–92% at five to ten years for appropriate candidates. At twenty years that figure falls to 44–62%, an honest reflection of the fact that osteoarthritis is a progressive condition and the realignment, however effective, does not halt the underlying disease permanently. For most patients who meet the selection criteria, however, the surgery can offer an active and relatively pain-free decade or more before joint replacement enters the picture.

Combining HTO with cartilage repair

Alignment correction alone addresses the mechanical problem — but where significant cartilage damage is already present, some patients are candidates for a combined approach in which osteotomy is paired with a cartilage restoration procedure.

The rationale is straightforward: cartilage repair in a varus knee is undermined from the outset. Without correcting the load distribution first, restored tissue in the medial compartment continues to be overloaded, compromising its durability. The osteotomy creates the mechanical environment in which biological repair can reasonably be expected to hold.

When the two strategies are combined, results are encouraging. In patients undergoing HTO alongside cartilage restoration — including marrow-stimulation procedures, biologic augmentation such as bone marrow aspirate concentrate (BMAC), and cell-based repair — up to 60% of deep cartilage lesions show partial or significant regeneration. Whether this translates to meaningfully longer TKR-free survival compared with osteotomy alone is not yet established, and evidence for combined regenerative protocols beyond medium-term follow-up remains limited.

The choice of repair technique determines the staging. Procedures that do not require prior cell harvest — such as matrix-augmented microfracture (AMIC) or BMAC augmentation — can generally be carried out in a single operative session alongside the osteotomy. Cell-based approaches such as ACI or MACI, which require a cartilage biopsy and a cultivation period of several weeks, typically follow a two-stage protocol: biopsy first, then repair and osteotomy combined in a subsequent procedure.

Which combination is appropriate depends on the size, grade, and location of cartilage damage confirmed at arthroscopy and on imaging — a determination that requires consultant-led assessment of each individual presentation.

Limitations and the longer-term picture

The honest picture for anyone weighing this decision is that HTO offers a meaningful but finite window. Around one in five patients will have converted to total knee replacement within a decade — a proportion that deserves candid pre-operative discussion, not retrospective discovery.

When TKR does eventually become necessary, prior osteotomy adds technical complexity. Changed bone anatomy, altered soft-tissue planes, and the presence of fixation hardware all require a surgeon experienced in post-osteotomy revision settings. This is not a reason to avoid the procedure, but it is a factor that belongs in the decision upfront.

Looking further ahead, genuine uncertainty remains. Whether realignment can arrest cartilage degeneration or only slow it is not yet resolved — and for combined regenerative protocols in particular, evidence beyond medium-term follow-up is limited. What the joint looks like at fifteen or twenty years is a question current data cannot fully answer. Patients considering HTO deserve to understand that ambiguity alongside the grounds for optimism: for appropriately selected individuals, the surgery has a well-evidenced record of delivering a substantially more active and less painful period before replacement becomes necessary.

The right next step for any individual depends on imaging, functional capacity, OA severity, and personal priorities — an assessment the MSK Doctors team can provide without a GP referral or waiting list at mskdoctors.com.

1. [1] High tibial osteotomy – Wikipedia. https://en.wikipedia.org/?curid=42896695 https://en.wikipedia.org/?curid=42896695