Can the ACL Heal? Operative versus Non-Operative Management of Anterior Cruciate Ligament Injuries in Athletes

Speakers: Dr Tom Cross, Sydney, Australia; Prof Ewa Maria Roos, Odense, Denmark; Prof Jacques Ménétrey, Geneva, Switzerland
Moderators: Kathrin Dettling, Winterthur & Dr Philippe Tscholl, Geneva, Switzerland
Congress: Sport & Exercise Medicine Switzerland and Swiss Sport Physiotherapy Association joint conference: “Structure & Function”, Lausanne, October 30^th and 31^st 2025

Scan to access presentation on Sportfisio YouTube channel

Introduction

The management of anterior cruciate ligament (ACL) injuries remains one of the most actively debated topics in sports medicine. While surgical reconstruction has been the dominant paradigm for decades, growing evidence supporting non-operative strategies has challenged this orthodoxy. At the 2025 Lausanne conference, three clinician-researchers convened to present their perspectives and confront their disagreements: Dr Tom Cross, a sports medicine physician from Sydney who developed the Cross Bracing Protocol (CBP); Professor Jacques Ménétrey, an orthopaedic surgeon from the University of Geneva; and Professor Ewa Roos, a physiotherapist-researcher from the University of Southern Denmark whose KANON trial was among the first RCTs comparing early ACL reconstruction with optional delayed reconstruction after structured rehabilitation. The session was moderated by Dr Philippe Tscholl, orthopaedic surgeon in Geneva, and Kathrin Dettling, a sports physiotherapist from Winterthur.

Facilitated Healing: The Cross Bracing Protocol

Dr Cross opened his presentation by framing the central question around two complementary “buckets” of knee stability: the static stabiliser (the ACL itself) and dynamic stabilisation (neuromuscular control and strength). His argument is that clinicians should aim to fill both, and that for a subset of injuries, the native ACL can be restored rather than replaced.
The CBP is grounded in a simple orthopaedic principle: reduction and immobilisation. When the knee is flexed beyond 90°, the torn ACL stumps are approximated within the intact synovial envelope, analogous to reducing a fracture. The protocol involves initial immobilisation in flexion (currently two weeks at 90°, reduced from four in the original protocol to mitigate arthrofibrosis), followed by sequential extension over several weeks with isometric strengthening throughout. Cross noted this was not entirely novel—Japanese investigators trialled extension-block bracing over 20 years ago, and the Jack brace attempted posterior drawer-based approximation—but these earlier approaches failed because they permitted weight-bearing and full motion, never achieving sustained reduction.
A critical contribution of Cross’s work is the classification of ACL injuries along a spectrum, much like fracture grading. Type 1 (non-displaced) injuries show intra-substance disruption without breach of the synovial envelope. Type 2 (displaced)—the so-called “Athlete’s ACL”, the most common pattern in high-energy pivoting injuries—features a gap with tissue displaced outside the intercondylar notch. Cross argued that triaging patients along this spectrum, using MRI to assess gap distance relative to ligament length, is essential: a gap-to-length ratio exceeding approximately 0.3 renders the injury “unreducible” by bracing. In his cohort of over 800 patients followed for one to eleven years, the re-rupture rate stands at 15%, with failures concentrated in those with thin or elongated healing patterns. He acknowledged that the biological quality of the healed tissue remains a key knowledge gap.

The Surgical Perspective: Personalised ­Decision-Making

Prof Ménétrey began his presentation with characteristic self-deprecating humour—“I’m the greatest surgeon in the world and I operate on all ACLs, period”—before immediately dismantling this caricature to illustrate how eminence-based medicine still pervades social media discourse despite robust evidence calling for nuance. His core message was that ACL management must be individualised, guided by a systematic assessment of injury severity, associated lesions, patient profile, and functional demands.
He highlighted several factors often underappreciated in the debate. First, epidemiological context matters: in Switzerland, the prevalence of alpine skiing produces injury patterns that differ from those in Australian football or Danish handball. Second, associated lesions are the rule rather than the exception—in his practice, approximately 80% of ACL tears present with concomitant pathology (meniscal tears, chondral lesions, peripheral instability), and new meniscal injury classifications now encompass root tears and subtle desinsertions previously underdiagnosed. Meniscal repair at the time of reconstruction improves ten-year outcomes, making a repairable meniscus a strong argument favouring surgery.
Ménétrey also drew a crucial distinction between return to sport and return to performance—noting that if cycling is the benchmark, virtually all patients “return to sport” within weeks, which obscures the real question of whether they can compete at their pre-injury level. He underscored that rotational laxity, assessed by the pivot shift test at three months, is his most important decision-making parameter. He also cautioned against over-reliance on MRI, presenting the case of a mountaineer whose ACL showed tissue continuity on imaging but was functionally incompetent and non-anatomically inserted at arthroscopy.

The Debate: Convergence, Contention and Open Questions

When to cross over to surgery

A central theme of the panel discussion was defining criteria for abandoning conservative management. Prof Roos advocated a patient-centered approach, relying heavily on what the patient reports about their functional limitations, supplemented by standard objective measures (strength, hop tests, contralateral comparison). Cross proposed a four-domain assessment: biological readiness (MRI healing quality, laxity testing), functional readiness (return-to-sport test batteries), psychological readiness (patient-reported confidence), and risk mitigation (correction of biomechanical deficits in landing and cutting). Ménétrey’s threshold was more binary: a persistent positive pivot shift at three months in a patient involved in cutting and jumping activities is, in his view, a strong indication for reconstruction.

The paediatric challenge

Dr Tscholl confronted the panel with the uncomfortable reality that surgical outcomes in patients under 15 are poor, with re-rupture or contralateral rupture rates approaching 30%. Ménétrey conceded that partial tears (his grades 1–2) can be managed non-operatively and acknowledged that the high re-rupture rate partly reflects past failures in addressing peripheral lesions and managing premature return to sport. He noted that the addition of extra-articular lateral tenodesis has begun to reduce re-rupture rates in this population. Cross argued that the CBP offers families a rational first-line option, noting that parents of young children rarely choose surgery first when presented with the alternative of attempting facilitated healing with the option of crossing over.

Secondary lesions: a surgical trump card?

Ménétrey raised the spectre of progressive meniscal and chondral damage in conservatively managed knees with residual instability. Roos countered with data from the KANON trial: when meniscal injuries addressed at the time of reconstruction are included alongside those developing later, there is no significant difference in total meniscal surgery rates between the early-reconstruction and rehabilitation-plus-optional-delayed-reconstruction arms. She noted that this nuance is often lost in cohort studies, which only report secondary injuries in the non-operative group. Cross reported that of 800 CBP patients followed beyond one year, only six required arthroscopy for meniscal symptoms despite 49% having some meniscal pathology at baseline—including ramp lesions, which he observed healing with flexion-based immobilisation.

Biology: healing versus scarring

The sharpest exchange concerned the biological nature of ACL “healing.” Ménétrey challenged Cross directly, arguing that while the ACL can form scar tissue with cell proliferation and revascularisation, this does not constitute true regeneration and should not be equated with fracture healing given the ACL’s inherently low biological capacity. Cross acknowledged the knowledge gap but drew an analogy with the medial collateral ligament—another ligament that heals with scar and is trusted for return to sport after bracing—arguing that the clinical question is whether the scar tissue is functionally adequate, not whether it is histologically identical to the native ACL. Both agreed that biopsies and histological studies of healed ACL tissue are urgently needed but unlikely to be obtained from patients.

Future Directions

Asked where they would invest an unlimited research budget, the panellists converged remarkably. Ménétrey prioritised prevention and biological enhancement of healing across all knee structures. Roos called for large, multi-country, multi-treatment registries that capture the full diversity of patients—not just elite athletes—and acknowledged the CBP as “the most revolutionary development in this field in a long time.” Cross echoed the call for international collaboration, drawing an analogy with oncology registries that pool data across centres. All three speakers agreed that neither operative nor non-operative management is universally superior, and that the field’s most pressing need is better tools—biological, imaging-based, and clinical—to match the right treatment to the right patient. As Tscholl summarised in closing: we can agree that not every ACL needs surgery, but we cannot yet agree on which ones do.

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