From Functional Recovery To Joint Protection — The Century-Long Evolution Of ACL Treatment Philosophy

From Functional Recovery to Joint Protection - The Century-Long Evolution of ACL Treatment Philosophy

The philosophy behind treating anterior cruciate ligament (ACL) injuries has undergone a prolonged evolution - from neglect, to functional restoration, to joint preservation. This history is not only a chronicle of technological progress, but also a deepening of medical understanding.

Phase One: Lack of Awareness and Passive Treatment (Pre-20th Century – 1960s)​

Before the function of the ACL was fully appreciated, treatment of knee injuries focused mainly on fractures and dislocations. At the end of the 19th century, German surgeon Paul Segond described a specific fracture pattern associated with ACL tears, yet failed to recognize the ligament's critical role. It was not until the early 20th century, with advances in knee biomechanics, that the ACL's function as the primary restraint to anterior tibial translation was gradually understood.

Even when an ACL tear was diagnosed during this period, treatment remained largely conservative. The prevailing view held that the powerful muscles surrounding the knee could compensate for ligament deficiency. Management typically involved plaster immobilization, muscle strengthening exercises, and bracing. However, many patients subsequently developed recurrent instability, meniscal injuries, and early joint degeneration.

In 1950, the renowned orthopedic surgeon O'Donoghue introduced the concept of the "unhappy triad," describing combined injuries to the ACL, medial collateral ligament, and medial meniscus. Still, treatment relied heavily on open surgical repair, with limited long-term success.

Phase Two: Dawn of Surgical Reconstruction and the Focus on Functional Recovery (1970s–1990s)​

The advent of arthroscopy in the 1970s revolutionized knee surgery. In 1970, Japanese surgeon Masaki Watanabe performed the first arthroscopic ACL reconstruction, ushering in a new era of minimally invasive procedures. However, the true breakthrough lay in the evolution of surgical philosophy.

In 1980, American surgeon David D. Drez Jr. proposed the concept of "functional ACL reconstruction," emphasizing the importance of isometric graft placement to maintain stability throughout the knee's range of motion. The central focus of this era was restoring mechanical stability - particularly to meet the demands of athletes returning to competition.

Graft selection also evolved. Initial preference for bone–patellar tendon–bone (BPTB) autografts was later joined by hamstring tendon grafts. In 1986, Rosenberg and Graf reported the first use of allogeneic tendons, expanding options for multiligament injuries and revision cases.

Nevertheless, research in this phase concentrated on short-term functional recovery - such as return-to-sport rates and stability scores - with limited attention to long-term joint protection.

Phase Three: Scrutiny of Long-Term Outcomes and Emerging Controversy (1990s–2010s)​

As patients who had undergone ACL reconstruction aged, long-term outcomes came under scrutiny. A Finnish 10-year follow-up study in 1996 found that, despite 90% patient satisfaction, radiographic osteoarthritis (OA) was present in 70% of cases - a revelation that shocked the sports medicine community.

Subsequent studies produced conflicting results. Some suggested ACLR did not reduce OA incidence compared to conservative treatment, while others reported protective effects. Discrepancies arose from small sample sizes, inadequate follow-up duration, inconsistent assessment criteria, and insufficient control of confounding variables.

A notable advance in this period was the establishment of standardized "return-to-play" criteria. In 2001, the International Knee Documentation Committee (IKDC) introduced standardized assessment tools, enabling comparison across studies. Yet, the emphasis remained on short- and mid-term functional restoration, with long-term joint preservation still a secondary concern.

Phase Four: Rise of Joint Protection Concepts and Evidence Accumulation (2010s–2020s)​

After 2010, with aging populations and rising quality-of-life expectations, joint preservation emerged as a central theme in ACL management. In 2014, a meta-analysis of over 5,000 patients found that ACLR reduced the risk of meniscal injury by 50% compared to conservative care. Since meniscal injury is a major OA risk factor, this indirectly implied a protective role for surgery.

A pivotal shift during this era was the redefinition of study endpoints. Earlier research favored subjective scores, laxity measurements, and radiographic grading - metrics weakly linked to long-term quality of life. Increasingly, researchers turned to "hard endpoints" such as total knee arthroplasty (TKA), an unambiguous marker of end-stage osteoarthritis.

In 2018, a nationwide Norwegian registry study first reported an association between ACLR and reduced TKA risk. However, limitations in sample size and confounding control left room for more definitive investigation.

Phase Five: Establishment of Evidence and the Paradigm Shift (2025–Present)​

The 2025 study by Ferdinand C. B. Ruelos et al., published in Arthroscopy, marks a turning point in ACL treatment philosophy. Its significance lies not only in its conclusions but also in its methodological rigor.

By leveraging a global large-scale database, the researchers obtained long-term follow-up data from nearly 12,000 patients - unprecedented in scale. Crucially, propensity score matching was used to control for dozens of confounders, including age, sex, race, obesity, diabetes, and hypertension, thereby minimizing bias.

The study demonstrated that ACLR significantly reduces the risk of future TKA, regardless of meniscal injury status. Notably, even in the subgroup with meniscal injuries treated by meniscectomy, the surgical group still exhibited a markedly lower TKA risk than the conservative group - challenging the traditional notion that meniscectomy negates any potential benefit of ACLR.

Historical Insights and Future Directions​

Reviewing this century-long trajectory reveals a clear evolution in ACL treatment philosophy: from early neglect, to a focus on functional recovery, to today's priority of joint preservation. This shift mirrors medicine's broader progression from "treating established disease" to "preventing future pathology," and from short-term gains to long-term quality-of-life optimization.

The historical significance of the Ruelos study lies in its provision of high-level evidence cementing the joint-protective value of ACLR. This is more than a therapeutic advance - it represents a fundamental change in mindset. Future historians may regard 2025 as the watershed year when ACL treatment shifted from debating "whether to operate" to exploring "how to optimize surgery for the best long-term outcomes."

As highlighted in expert commentary, the next pivotal question is whether preserving - rather than resecting - the meniscus during ACLR can further enhance joint protection. This inquiry will likely usher in a new stage of sports medicine research centered on tissue preservationand biological augmentation.

History advances through cycles of negation and renewal. The evolution of ACL treatment philosophy embodies this dialectical progression, wherein each stage builds upon its predecessors while paving the way for future breakthroughs. In this sense, history is not merely a record of the past, but a compass for the future.

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