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Ligamento Cruzado Anterior

ACL Tear — Do I Need Surgery?

An anterior cruciate ligament tear is one of the most common knee injuries. The decision to operate is not automatic — it depends on you, your knee and your lifestyle.

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~200 000Tears/year in Europe
70–80%Sports injuries
9–12 mesesReturn to sport
90–95%Reconstruction success
What is the ACL

The Ligament that Stabilises the Knee

The anterior cruciate ligament (ACL) is one of the most important structures for knee stability. It controls the anterior translation of the tibia relative to the femur and resists internal rotation — movements essential to changes of direction, braking and jumping.

An ACL tear typically occurs through sudden deceleration, pivoting or contact with another player. Patients often hear or feel a "pop", followed by acute pain and rapid swelling of the knee.

Each episode of instability — the feeling of the knee "giving way" — can cause further injury to the menisci and cartilage. For this reason, the treatment decision should not be postponed indefinitely.

An ACL tear rarely heals on its own. Without appropriate treatment, an unstable knee accumulates secondary injuries that worsen the long-term prognosis.

Treatment Decision

Surgery or Conservative Treatment?

This is the central question in an ACL tear. The answer is not universal — it depends on individual factors that the specialist will assess in consultation.

✓ Conservative Treatment

  • Low level of physical activity (sedentary)
  • Stable knee with no episodes of instability
  • No associated meniscal or ligament injuries
  • Older age with low functional demands
  • Patient declines the surgical / anaesthetic risk
  • Acute phase with severe AMI — stabilisation may be needed first

→ Surgical Reconstruction

  • Active patient with recurrent instability
  • Athlete in pivoting sports (football, basketball, skiing)
  • Associated meniscal or chondral injuries to treat
  • Failure of conservative treatment
  • Young patient with high expectations of returning to sport
  • Combined multi-ligament injury
Clinical note: Current research (2024 systematic review) shows that conservative treatment can be appropriate for selected patients — but the risk of secondary meniscal and chondral injury in unstable knees is real and cumulative. The decision requires an individualised assessment.
Surgical Technique

Graft Types for ACL Reconstruction

ACL reconstruction uses a tendon graft to replace the ligament. The choice of graft is individualised and influences the long-term outcome.

Hamstrings (Semitendinosus)

The most commonly used graft. Low harvest morbidity, good mechanical strength. Can be combined with gracilis for greater volume.

Most used

Patellar Tendon (BTB)

Bone-tendon-bone graft. Faster bone integration — favoured in elite sport and high-demand primary reconstructions.

Elite sport
⬆

Quadriceps Tendon

Increasingly used. Large graft volume, acceptable morbidity, good integration. A valid option especially in older patients.

Growing trend

Bank Graft (Allograft)

Donor tissue. No harvest morbidity — reserved for revisions or specific situations with a shortage of autologous graft.

Revisions / complex cases
Protocol of Excellence

SANTI Protocol — Anterolateral Tenodesis

The SANTI protocol (developed by Prof. Bertrand Sonnery-Cottet) integrates the assessment and treatment of arthrogenic muscle inhibition (AMI) into the ACL surgical protocol — an outcome differentiator that few centres apply systematically.

01

Pre-operative AMI Assessment

Grading of quadriceps inhibition before surgery. In selected cases, surgery is postponed until the AMI resolves.

02

Surgery + Lateral Ligamentoplasty

ACL reconstruction combined, when indicated, with extra-articular tenodesis (Lemaire technique or Anterolateral, refined by Sonnery-Cottet) for rotational control.

03

Post-op Neuromotor Rehabilitation

Quadriceps reactivation protocol and treatment of residual AMI from the first post-operative day.

Learn more about AMI (quadriceps inhibition) →
Rehabilitation

Milestone by Milestone — Return to Sport

Early return before 9 months is associated with a higher risk of re-tear. Strength and functional criteria matter more than time alone.

Dia 1
Walking with crutches. Quadriceps activation.
2–4 sem
Walking without support. Extension and flexion to 90°.
6 sem
Stationary bike. Progressive strengthening.
3–4 meses
Straight-line running. Advanced proprioception.
6 meses
Changes of direction. Isokinetic strength testing.
9–12 meses
Return to contact sport after validated criteria.
Frequently Asked Questions

Questions about the ACL

Not necessarily. Imaging does not replace clinical assessment. Patients with stable knees and low sporting demands can be treated conservatively with success. The decision depends on activity level, the presence of instability and associated injuries.
Optimal timing depends on the presence of arthrogenic muscle inhibition (AMI) and joint effusion. Operating with severe AMI or a very inflamed knee increases the risk of arthrofibrosis. In many cases it is preferable to wait 3–6 weeks after the acute injury to regain range of motion and muscle activation before surgery.
There is no universally superior graft. The patellar tendon (BTB) has faster bone integration and is often preferred in elite sport. The hamstrings have lower harvest morbidity. The quadriceps tendon is gaining popularity. The choice should be individualised with your surgeon.
Yes — the great majority of patients return to their pre-injury level of sport. Return to contact football is typically between 9 and 12 months, conditional on meeting strength criteria (>90% quadriceps symmetry) and validated functional tests. Early return before 9 months significantly increases the risk of re-tear.
Extra-articular tenodesis (the Lemaire technique or Anterolateral, refined by Sonnery-Cottet) is a procedure added to ACL reconstruction to control excessive internal rotation of the knee. Today its indications cover a wide range of clinical cases — not just a few selected patients: they lower the ACL re-rupture rate and protect repaired menisci, and have become one of the main "rediscoveries" in knee surgery in recent years. It is indicated in patients with hyperlaxity, high-rotation sports or a history of significant instability. It is not applied in every case.
Rehabilitation is progressive over several months: walking and daily activities in the first weeks; running around 3–4 months; and return to pivoting/contact sports usually between 9 and 12 months — governed by strength, stability and functional-test criteria, not by time alone.
For everyday activities, many people can, especially after strengthening the stabilising muscles. The problem arises with rotation/change-of-direction movements, where the knee may "give way" (instability), increasing the risk of associated injuries (meniscus, cartilage). That is why, in young or active people, reconstruction is generally recommended.
Yes. Neuromuscular exercise programmes — strengthening, control of dynamic knee valgus, plyometrics and landing/change-of-direction technique — have been shown to reduce the risk of ACL injury, particularly in athletes. These exercises are also an essential part of rehabilitation to prevent re-injury after reconstruction.
NC

Dr. Nuno Camelo Barbosa

Orthopaedic Surgeon · Knee Subspecialist
Hospital Lusíadas Porto · Hospital Misericórdia Vila do Conde · Paços de Ferreira

ACLExtra-articularLigament stability

Have you had an ACL injury?

The decision between surgery and conservative treatment requires a specialist in-person assessment. Book your appointment in Porto, Paços de Ferreira or Vila do Conde.

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References

Clinical guidelines and scientific reviews supporting this information.

  1. AAOS Clinical Practice Guideline — Management of Anterior Cruciate Ligament Injuries. American Academy of Orthopaedic Surgeons, 2022.
  2. Management of ACL revision: the 2022 ESSKA consensus. Knee Surg Sports Traumatol Arthrosc, 2023.
  3. Watson SL, et al. ACL Injury Risk Reduction: Demonstration of Key Exercises. Video Journal of Sports Medicine, 2025. PMID 41209365.
  4. Remnant preservation may improve proprioception after anterior cruciate ligament reconstruction. Journal of Orthopaedics and Traumatology, 2022. PMID 35478294.
Dr. Nuno Camelo Barbosa
Dr. Nuno Camelo Barbosa
Orthopaedic surgeon · Knee surgery subspecialty
Peer reviewer (AJSM · KSSTA · OJSM · JEO)
Last medically reviewed: 24 July 2026
Full profile  ·  Book appointment →

Surgical Video

SAMBBA — ACL reconstruction