When ankle OA reaches the surgical threshold

Being told your ankle osteoarthritis is 'advanced' or 'end-stage' usually means one thing in practice: the cartilage cushioning the joint has worn away to the point where bone is moving against bone, causing persistent pain, stiffness, and a level of functional loss that has stopped responding to non-surgical treatment. That functional loss — difficulty walking, standing, or managing stairs — is as important to the clinical picture as pain alone. Surgery is not triggered by imaging findings in isolation; it follows a structured conservative trial, typically of at least six months, involving physiotherapy, orthotic bracing, activity modification, anti-inflammatory medication, and injections where appropriate.

Once that threshold is crossed, two main surgical routes exist: ankle fusion (arthrodesis), which permanently locks the joint to eliminate pain, and total ankle replacement (TAR), which resurfaces the joint and aims to preserve motion. For patients with less advanced disease, intermediate joint-preserving procedures — such as osteotomy or distraction arthroplasty — may delay or avoid either, but they fall outside the scope of what this article addresses.

One important caveat worth setting out early: ankle OA has a considerably thinner evidence base than hip or knee OA. Much of the guidance clinicians use is extrapolated across joints, and no single validated clinical practice guideline for ankle OA management yet exists. The evidence reviewed here is the best currently available — but readers should understand the field is still maturing.

The conservative trial that comes before surgery

A six-month conservative trial sounds procedural, but in practice it unfolds as a staged programme built around several concurrent strategies. Physiotherapy centres on strengthening the muscles that support the ankle — reducing load on the damaged joint surface — alongside gait retraining and flexibility work. Custom orthotics or braced footwear redistribute weight and limit painful end-range movement. Activity modification means identifying which movements drive symptoms and substituting lower-impact alternatives; for many patients, this alone provides meaningful relief.

Pharmacological support runs alongside. NSAIDs address inflammatory flares, and intra-articular injections offer more targeted options. Corticosteroid is often the first injection choice, acting quickly to settle acute symptoms; hyaluronic acid (HA) supplements the joint's natural lubrication; and platelet-rich plasma (PRP) and related orthobiologic preparations are used when earlier measures have not sustained improvement. A 2026 Delphi consensus, involving 75 experts across 25 countries, affirmed that these orthobiologics represent a reasonable bridge between conservative care and surgical planning — though no single formulation has demonstrated superiority over another.

Injections also carry an underappreciated diagnostic role. A clear, short-lived response to intra-articular local anaesthetic helps confirm the ankle joint itself — rather than an adjacent tendon, nerve, or subtalar structure — as the dominant pain source, which matters before surgery is committed to.

Throughout, the purpose is not to defer a decision indefinitely. The conservative phase is the stage at which the surgical indication is confirmed, joint status is optimised where possible, and both patient and clinician can be confident the threshold for intervention has genuinely been reached.

Joint-preserving options before end-stage surgery

Between injections and end-stage surgery lies a narrower but real middle ground for patients whose OA is advancing but has not yet reached full bone-on-bone destruction.

Osteotomy realigns the bones around the ankle to redistribute load away from the most damaged cartilage compartment. Where abnormal alignment is a meaningful driver of focal wear, correcting it may slow progression and delay the need for more definitive intervention.

Distraction arthroplasty applies an external fixator frame to unload the joint over several months. The intention is that removing compressive stress allows some degree of biological recovery at the joint surface — a form of structured rest rather than active repair.

Both procedures are performed at specialist orthopaedic centres, but they are considerably less common than fusion or TAR in routine practice, and many general orthopaedic units refer patients to higher-volume centres where the techniques are regularly used. Candidacy is narrow: primarily younger patients for whom the trade-offs of early fusion or replacement are considered disproportionate at their stage of life. The evidence underpinning both options remains largely observational — cohort series and expert consensus rather than randomised trials — and this is a recognised gap that limits the strength of any current recommendation.

What the evidence shows for total ankle replacement

The TARVA trial remains the most rigorous head-to-head evidence available. Conducted across 17 UK centres and enrolling 303 patients aged 50 to 85, it compared TAR with ankle fusion at 52 weeks using a validated walking and standing function score. The headline result: both procedures produced similarly large improvements, with no statistically significant difference between groups overall (adjusted difference −5.6 points, 95% CI −12.5 to 1.4; p=0.12).

A post-hoc analysis within TARVA, however, points to something clinically important about implant design. When only fixed-bearing TAR devices were examined — distinct from mobile-bearing designs — the advantage over fusion became both meaningful and statistically significant (−11.1 points, 95% CI −19.3 to −2.9; p=0.008). This is a subgroup finding from a post-hoc analysis, not a pre-specified primary result, so it warrants some caution; but it suggests implant choice is a variable worth discussing with a surgeon before any commitment is made. Health-economic modelling attached to TARVA estimated a 69% probability that TAR represents better NHS value over a patient's lifetime, based on combined quality-of-life and cost projections — though modelling assumptions, rather than observed lifetime data, underpin that figure.

For longer-term outcomes, the COFAS prospective cohort — 211 patients with a minimum ten years of follow-up (mean 13.2 years) — found functional results broadly similar between the two procedures, but with a higher rate of further surgery in the TAR group (42% vs 30%; p=0.02). This nuance matters: TAR preserves motion, but that complexity comes with a marginally greater likelihood of returning to theatre over a decade.

Reoperation rates across implant generations tell a more encouraging story. German nationwide data show that early-cohort TAR (2001–2002 era) carried roughly double the unplanned reoperation rate of fusion at ten years (38% vs 19%). In a later cohort (2006–2007), rates had converged to near parity — 23% for TAR versus 21% for fusion — attributed to improvements in implant design, surgical technique, and patient selection.

One advantage of motion preservation that functional scores at one year are unlikely to capture is the effect on adjacent joints. Gait analysis shows measurably increased subtalar joint loading during early stance after arthrodesis; TAR, by maintaining ankle movement, distributes these forces more symmetrically. For patients who already have some adjacent joint wear, this biomechanical difference has real clinical weight.

Fusion's reliability and long-term trade-offs

Ankle arthrodesis has decades of surgical history behind it, and for a substantial proportion of patients it remains the most appropriate and reliable choice. Permanently eliminating the damaged joint surface resolves the primary source of pain, and the absence of a prosthetic implant — with its potential for wear, loosening, or mechanical failure — gives fusion a predictability that TAR cannot quite match in a single operation.

Durable functional benefit is well-established. In a US multisite prospective cohort of 517 patients followed for eight years, both fusion and TAR maintained large improvements over pre-operative levels — a mean 27-point gain on the FAAM activities of daily living scale and an 8.6-point improvement in SF-36 physical component scores — with no meaningful divergence between the two procedures at that time horizon.

The main intra-operative risk specific to fusion is non-union: the bones fail to knit together as intended. Radiographically, this occurs in approximately 12.1% of cases; around 7.1% of patients experience symptoms from it. Roughly one in eight patients, in other words, may show incomplete fusion on imaging, though not all will be troubled by it. Pre-operative discussion of this risk, and the factors that influence it — bone quality, comorbidities such as diabetes, smoking — is an important part of consent.

The longer-term biomechanical consideration, as noted in the TAR section, is increased loading on the subtalar and neighbouring joints. This is clinically important in patient selection: where adjacent joint arthritis is already present before surgery, fusion generally becomes inadvisable, because removing ankle motion concentrates mechanical stress precisely onto joints that are already compromised. In that scenario, TAR is typically the preferred route.

For patients whose adjacent joints remain healthy and whose lifestyle demands durability over motion, fusion offers a genuine and well-supported surgical solution — a point that matters when weighing which procedure best fits an individual's circumstances.

Matching the procedure to the patient

Two broad patient profiles emerge from the evidence, though neither maps cleanly onto a checklist.

TAR is generally suited to older or less physically demanding patients with stable ankle alignment, good underlying bone stock, and intact adjacent joints. The preservation of ankle motion is the central advantage — both for day-to-day function and, as the gait biomechanics data established in the preceding section demonstrate, for reducing long-term stress on neighbouring joints. Where adjacent joint arthritis is already present before surgery, that biomechanical argument tips the balance firmly toward replacement; restating the mechanism here would be repetition.

Fusion is generally preferred for younger patients, those in manual or physically demanding occupations, and anyone with vascular compromise, severe peripheral neuropathy, or significant foot deformity that makes reliable implant positioning difficult. The single-operation predictability of arthrodesis — no prosthetic component to wear or loosen — carries real weight for patients whose activity levels or anatomy make long-term implant durability uncertain.

Neither profile is a protocol. No validated clinical tool currently exists for determining TAR candidacy; selection rests on specialist assessment integrating weight-bearing imaging, functional evaluation, bone quality, and an honest conversation about occupation, activity targets, and what each procedure realistically delivers. A patient whose priority is returning to a physically demanding trade is having a materially different conversation from one whose goal is comfortable everyday walking.

Recovery from both procedures is measured in months rather than weeks. Fusion typically involves a period of non-weight-bearing while the bones consolidate; TAR recovery centres more on wound healing and implant integration. Progression in both cases is guided by functional criteria — restored limb confidence, movement symmetry, and graded load tolerance — rather than fixed dates. Pre-operative comorbidities such as diabetes and smoking influence healing trajectories considerably.

For patients at this decision point, a specialist assessment drawing on imaging, clinical history, and patient goals is the appropriate next step; consultations can be arranged at londoncartilage.com.

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2. [2] Outcomes of Total Ankle Replacement Versus Ankle Arthrodesis — COFAS Long-term Cohort (JBJS 2024). (2024). https://doi.org/10.2106/JBJS.24.00361 https://doi.org/10.2106/JBJS.24.00361
3. [3] Utilization and Medicare Reimbursement for TAR and Ankle Arthrodesis 2010–2021 (2024). (2024). https://doi.org/10.1177/2473011424s00468 https://doi.org/10.1177/2473011424s00468
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