ACL rupture — how Dr Mooney uses the latest evidence in managing these devastating injuries

A rupture that changes everything

For a young footballer sprinting towards goal, a netballer cutting across court, or a skier carving through a turn, an ACL rupture arrives without warning. A pivot, a landing, a sharp change of direction — and then a pop, a giving way, and a knee that is suddenly, completely unreliable. For athletes in particular, it is one of the most psychologically and physically disruptive injuries in sport.

The anterior cruciate ligament is not a large structure — roughly the size of a finger — but it is the primary restraint to forward movement of the shin bone on the thigh bone, and the key controller of rotational knee stability. When it ruptures, that stability disappears. The knee that once responded instinctively to every athletic demand becomes a liability.

The good news is that outcomes from modern ACL surgery, when combined with thorough rehabilitation, are better than they have ever been. But the decisions that surround it — whether to operate, which graft to use, whether to add a lateral extra-articular tenodesis (LET) — are not simple ones, and they are not the same for every patient. What follows is an account of how I think through those decisions in 2026.

Not every ACL tear requires surgery

This is the first and most important point, because it runs counter to what many patients expect when they arrive having been told their ACL is torn. Surgery is not automatic. The right treatment depends on the patient in front of you — their age, their activity demands, the stability of their knee, and any associated injuries.

For a 45-year-old recreational walker with a stable knee and no interest in returning to pivoting sport, a well-structured physiotherapy programme may be entirely appropriate. Multiple studies have shown that carefully selected patients — often called “copers” — can achieve excellent functional outcomes without surgery. Surgery remains an option for the future, should functional goals not be achievable with the ACL deficient knee.

For a 19-year-old AFL player, the calculus is entirely different. Returning to high-level pivoting sport with a deficient ACL carries a significant risk of further meniscal damage from repeated giving-way episodes, accelerated joint deterioration, and ultimately a more complex surgical problem down the track. In this patient, surgery is usually the right recommendation, but in this case the nuance lives in the graft type decision, and whether additional stabilisation procedures such as the LET procedure are employed.

The right treatment is not always surgery — but for a young athlete who wants to return to pivoting sport, reconstruction gives the knee its best chance at a long and functional future.

The consultation is where this decision is worked through carefully. Defining the athlete's goals: I want to understand what the patient is trying to get back to, what their knee feels like on a day-to-day basis, and what the MRI shows in terms of associated meniscal and cartilage damage. The decision is made together, not me making the decision for the patient.

Timing: why I rarely rush to the operating theatre

When surgery is agreed upon, the timing matters. Operating on an acutely swollen, stiff knee — particularly within the first two to three weeks of injury — significantly increases the risk of post-operative stiffness and scarring of the joint (arthrofibrosis). This is one of the most preventable complications in ACL surgery, and it is largely avoided by delaying the procedure until the acute inflammatory phase has resolved.

My preference is to operate once the swelling has settled, full passive extension has returned, and the patient has achieved at least 120 degrees of flexion. This typically takes four to six weeks. During this time, I strongly encourage patients to commence physiotherapy and pre-operative conditioning — a period of “prehabilitation” that consistently produces better post-operative outcomes.

Choosing the right graft

ACL reconstruction rebuilds the torn ligament using a tendon graft taken from elsewhere in the body. There are three main options, and the evidence does not decisively favour any single one over the others in terms of overall outcome. What the evidence does show is that each has distinct advantages and trade-offs, and the right choice is individual.

Hamstring tendon (gracilis and semitendinosus) remains the most commonly used graft in Australia. It produces a strong, reliable reconstruction with minimal anterior knee pain and a small harvest scar. The main consideration is hamstring weakness in the early post-operative period, which resolves with progressive rehabilitation in the majority of patients.

Quadriceps tendon has grown significantly in popularity over the past five years. It provides excellent graft volume — often larger than hamstring — and avoids any hamstring morbidity. It is particularly useful in patients with smaller hamstring tendons, larger body size, or when the hamstring has already been used in a prior reconstruction. The evidence base is building rapidly and results are very encouraging.

Patellar tendon (bone-patellar tendon-bone, or BPTB) has historically been considered the gold standard, particularly in elite sport. It heals bone-to-bone, which is technically the fastest graft incorporation, and has the longest outcome data of any graft. The significant trade-off is anterior knee pain, which affects up to 20% of patients and can be persistent. For patients who kneel regularly — trades, some sports — or who have pre-existing anterior knee problems, this is an important consideration.

The decision is made with the patient after discussing their anatomy, their sport, and what matters most to them in the recovery. There is no universally correct answer.

When I add LET — and why

Lateral extra-articular tenodesis, or LET, is an additional procedure performed at the same time as ACL reconstruction in selected patients. It has been one of the most significant developments in ACL surgery over the past decade, and the evidence behind it is now compelling.

The problem LET addresses is rotational instability. Even after a technically well-performed ACL reconstruction, the intra-articular graft alone does not fully control rotation in all patients — particularly in those with generalised ligamentous laxity, high-grade pre-operative pivot shift, or a steep lateral tibial slope. In these patients, residual rotational laxity persists, and the stress on the newly reconstructed ACL graft is higher as a consequence. The re-tear rate in this group, particularly in young athletes returning to pivoting sport, can be alarmingly high.

The STABILITY trial, published in the New England Journal of Medicine in 2022, was a landmark moment. This multicentre randomised controlled trial demonstrated that adding LET to hamstring graft ACL reconstruction in young, active patients reduced the risk of ACL graft re-tear by more than 40% compared to ACL reconstruction alone. For a 17-year-old returning to football, this is a clinically meaningful difference.

The STABILITY trial changed practice. For young, high-demand patients with significant rotational instability, I now routinely add LET — not as a belt-and-braces measure, but because the evidence clearly supports it.

The technique I use is the Arnold and Coker modified LET. It uses a strip of the iliotibial band — which remains attached distally at Gerdy’s tubercle — routed beneath both the popliteal tendon and the fibular collateral ligament before being fixed to the lateral femoral condyle. This routing path is anatomically important: it recreates the restraint function of the anterolateral ligament complex without sacrificing the native collateral structures.

Adding LET does not substantially change the overall recovery timeline. There are modest modifications to early rehabilitation — particularly avoiding aggressive tibial internal rotation and forceful iliotibial band stretching in the first four to six weeks — but patients with LET generally return to sport at the same timeframe as those without it. The benefit is a meaningfully lower risk of re-tearing something that took nine months to build.

I consider LET for patients who are under 25 and returning to high-level pivoting sport, those with Grade 2 or 3 pivot shift on pre-operative examination, patients with generalised ligamentous laxity, anyone undergoing revision ACL reconstruction, and cases with a steep lateral tibial slope on imaging.

The rehabilitation that makes surgery worthwhile

Surgery is only the beginning. The outcome of ACL reconstruction is determined in large part by what happens over the following nine to twelve months. This is not a minor point: the biology of graft maturation — the process by which the transplanted tendon transforms into functional ligament tissue — takes approximately twelve months. Returning to contact sport before that process is complete significantly increases re-tear risk, regardless of how the knee feels.

Rehabilitation is divided into progressive phases, each with defined goals and criteria for advancement. The early phase focuses on controlling swelling, restoring range of motion, and re-establishing quadriceps activation — the most important muscle group for knee stability. The middle phase builds strength systematically, with particular attention to the hamstrings, quadriceps, and hip stabilisers. The later phase introduces running, then plyometrics, then sport-specific training, with each stage gated by objective criteria rather than time alone.

Phase	Timeframe	Goals
1 — Protection & Early Recovery	Weeks 0–2	Control pain and swelling. Restore full passive extension. Achieve 0–90° flexion. Re-establish quadriceps activation. Walk with crutches.
2 — Mobility & Neuromuscular Activation	Weeks 2–6	Achieve full range of motion (0–130°+). Progress to full weight bearing without crutches. Restore normal gait. Begin proprioception and balance retraining.
3 — Strength Foundation	Weeks 6–12	Eliminate residual swelling. Build lower limb strength symmetry. Achieve single-leg squat control. Develop cardiovascular fitness in preparation for running.
4 — Progressive Loading & Return to Running	Months 3–6	Return to straight-line running. Introduce double-leg plyometric foundations. Build limb symmetry on strength testing (>80%). Begin sport-specific movement preparation.
5 — Sport-Specific Conditioning	Months 6–9	Return to non-contact team training. Complete cutting, pivoting, and reactive agility progressions. Achieve single-leg hop test symmetry (>90%). Assess psychological readiness.
6 — Return to Sport	Months 9–12	Return to full contact training and competition once all criteria are met: minimum 9 months from surgery, limb symmetry index >90%, psychological readiness, and surgeon clearance.

Return to sport requires meeting a set of measurable benchmarks: a limb symmetry index of 90% or greater on strength and hop testing, full psychological readiness assessed by a validated score (the ACL-RSI), and clearance from both the physiotherapist and the surgeon. Patients who return only when they meet these criteria have substantially lower re-tear rates than those who return by time alone.

What patients can realistically expect

Approximately 85% of patients who undergo ACL reconstruction return to some level of sport. Around 65% return to their pre-injury level of competition. The overall graft re-tear rate is 5–10%, with higher rates in younger athletes; in carefully selected patients who receive LET, this risk is substantially reduced.

Long-term, both ACL-deficient and ACL-reconstructed knees carry a higher risk of osteoarthritis than uninjured knees. This risk is largely driven by the cartilage and meniscal damage that occurred at the time of the original injury — not by the reconstruction itself. Maintaining strong leg muscles, completing the full rehabilitation programme, and using an ACL prevention warm-up on return to sport are the best tools patients have to protect their joints in the long term.

ACL surgery has come a long way. The decisions around it have become more nuanced, not less — and that is a good thing. Getting them right, for the right patient, at the right time, gives a young athlete the best chance of returning to the sport they love with a knee that is as resilient as we can make it.