ACL Reconstruction

What is ACL Reconstruction?

Anterior cruciate ligament (ACL) reconstruction is an operation used to restore stability to a knee after an ACL tear. The damaged ligament is replaced with a graft, usually a tendon taken from another part of the patient's own body.


Reconstruction may be considered when an ACL-deficient knee remains unstable, when a patient wants to return to pivoting or high-demand activities, or when other knee injuries influence treatment.


Not every ACL tear requires reconstruction. The decision depends on knee stability, symptoms, associated injuries, activity requirements and the patient's goals.


For information about the injury itself, including symptoms, partial and complete tears and diagnosis, see ACL Tear.


Key Points

  • ACL reconstruction replaces the damaged anterior cruciate ligament with a graft.
  • Reconstruction is not required for every ACL tear.
  • Surgery may be considered when instability interferes with sport, work or everyday activities.
  • Prehabilitation can help restore movement, reduce swelling and improve strength before surgery.
  • Hamstring, patellar tendon and quadriceps tendon autografts are commonly considered.
  • Rehabilitation and return-to-sport testing are important parts of treatment and commonly continue for many months.


When may ACL reconstruction be considered?

ACL reconstruction may be considered when an ACL tear results in ongoing functional instability or when future activities place substantial pivoting and rotational demands on the knee.


Factors that may support consideration of reconstruction include:

  • Repeated episodes of the knee giving way
  • Difficulty returning to pivoting or cutting sports
  • Participation in sports such as football, soccer, netball, basketball or skiing
  • Physically demanding work requiring turning, climbing or unpredictable movements
  • Associated meniscus or other ligament injuries
  • Failure to achieve adequate functional stability with rehabilitation
  • A desire to return to high-demand sporting activities


Instability means the knee feels as though it shifts, buckles, or gives way, particularly during turning, pivoting, or sudden changes of direction.


Age alone does not determine whether reconstruction is appropriate. Biological age, knee condition, activity level, expectations and associated injuries can all influence the decision.


When may ACL reconstruction not be required?

Some patients can achieve satisfactory knee function without ACL reconstruction, particularly when the knee remains stable during the activities that matter to them.


A period of rehabilitation can sometimes help determine whether the knee is functionally stable enough without reconstruction.


The decision should therefore be individual rather than based simply on whether an MRI shows a complete ACL tear.


For more information about non-operative management, see ACL Tear Without Surgery.


What is prehabilitation before ACL reconstruction?

Prehabilitation is rehabilitation performed before surgery to prepare the knee and the patient for ACL reconstruction.


Immediately after an ACL injury, the knee may be swollen, stiff and weak. Surgery is not necessarily performed while the knee remains acutely inflamed.


Prehabilitation commonly aims to:

  • Reduce swelling
  • Restore full knee extension
  • Improve knee flexion
  • Restore a normal walking pattern
  • Improve quadriceps activation
  • Strengthen the surrounding muscles
  • Prepare the patient for postoperative exercises


The amount of prehabilitation required varies. Some patients regain suitable knee function relatively quickly, while others need longer before surgery.

Evidence-based rehabilitation guidance suggests that preoperative rehabilitation may improve early postoperative movement and quadriceps strength. (British Journal of Sports Medicine)


What happens during ACL reconstruction?

The damaged ligament is replaced with a graft positioned within the knee to reproduce the stabilising function of the ACL.


The main surgical steps commonly include:

  1. Arthroscopic assessment
    The surgeon inserts a camera into the knee to assess the joint, including the menisci and cartilage.
  2. Graft preparation
    The selected tendon graft is harvested and prepared for reconstruction.
  3. Preparation of the ACL attachment sites
    Bone tunnels or sockets are created in the tibia and femur at the planned graft positions.
  4. Graft placement
    The graft is passed into position through the prepared bone tunnels or sockets.
  5. Graft fixation
    The graft is secured to the femur and tibia using appropriate fixation devices.
  6. Assessment of the reconstruction
    Graft position, tension, knee movement and stability are assessed.
  7. Treatment of associated injuries where required
    Meniscus or cartilage injuries may sometimes be treated during the same operation.
  8. Closure
    The small surgical incisions are closed, and dressings are applied.


Specific surgical techniques and fixation methods can vary based on the patient, graft, and surgeon's assessment.


What grafts can be used for ACL reconstruction?

A graft is the tissue used to create the new ACL. Autografts taken from the patient's own body commonly include hamstring tendon, patellar tendon and quadriceps tendon grafts.


For a more detailed comparison and information about how graft selection is individualised, see ACL Graft Options.


Can other knee injuries be treated during ACL reconstruction?

Yes. Meniscus, cartilage or other ligament injuries identified before or during ACL reconstruction may sometimes require treatment during the same procedure.


The meniscus is a C-shaped structure of fibrocartilage that helps distribute load and absorb forces within the knee.


Associated procedures may include:

  • Meniscus repair
  • Treatment of some meniscus tears
  • Assessment or treatment of articular cartilage injuries
  • Treatment of other ligament injuries when required


Whether another procedure is needed depends on the type, location and severity of the associated injury.


A meniscus repair can also influence postoperative rehabilitation because the repaired tissue may need additional protection while it heals.


How long will I stay in the hospital?

ACL reconstruction is commonly performed as day surgery, although some patients may stay overnight depending on the operation, associated procedures, and individual circumstances.


Before discharge, the clinical team will generally check that pain is adequately controlled and that the patient can mobilise safely.


A physiotherapist may provide instructions regarding:

  • Crutch use
  • Weight bearing
  • Early knee movement
  • Home exercises
  • Swelling management
  • Safe walking


The existing practice information describes ACL reconstruction as either a day procedure or overnight admission.


What are the risks of ACL reconstruction?

ACL reconstruction is commonly performed successfully, but all surgery carries potential risks and complications.


Possible risks include:

  • Infection
  • Blood clots
  • Bleeding
  • Nerve or blood vessel injury
  • Knee stiffness
  • Persistent pain
  • Loss of movement
  • Ongoing instability
  • Graft stretching or failure
  • Reinjury
  • Problems related to the graft-harvesting site
  • Further meniscus or cartilage problems
  • Need for additional surgery


The likelihood of an individual complication varies with patient factors, the injury, and the procedure.


Dr Hayes can discuss the risks relevant to the individual patient before surgery.


What happens after ACL reconstruction?

Early recovery focuses on controlling pain and swelling, regaining knee movement, restoring muscle activation and walking safely.


Initially, treatment may involve:

  • Pain relief
  • Ice and swelling management
  • Wound care
  • Crutches where required
  • Early exercises
  • Gradual restoration of knee movement
  • Quadriceps activation
  • Physiotherapy


Postoperative instructions may differ if additional procedures, such as meniscus repair, have been performed.


Patients should follow the specific instructions provided by their surgical and physiotherapy team rather than relying on a generic timetable.


What is the ACL reconstruction recovery timeline?

Recovery occurs progressively over many months, moving from wound healing and basic knee function to strength, running, agility and potentially a return to sport.


For a more detailed stage-by-stage guide, see ACL Reconstruction Recovery Timeline.


Why is ACL Rehabilitation important?

Rehabilitation is essential to ACL reconstruction because surgery restores the ligament structure but does not, by itself, restore strength, movement, coordination, or sporting ability.


A structured program generally progresses through:

  • Restoring knee extension and flexion
  • Reducing swelling
  • Regaining quadriceps strength
  • Improving hamstring and hip strength
  • Balance and movement-control exercises
  • Running preparation
  • Plyometric or jumping exercises
  • Landing control
  • Agility and change-of-direction training
  • Sport-specific conditioning


Modern ACL rehabilitation is increasingly criteria-based. This means patients progress when they reach appropriate physical milestones rather than simply because a certain number of weeks has passed.


Exercise remains the mainstay of rehabilitation after ACL reconstruction. (British Journal of Sports Medicine)


For detailed information about the rehabilitation stages and exercises, see ACL Rehabilitation.


How is return to sport assessed?

Return to sport should generally involve assessing knee function, strength, movement quality, sport-specific ability, and psychological readiness rather than relying on time since surgery alone.


Time remains relevant because the graft undergoes biological healing, but time alone cannot establish whether an athlete is ready to return.

For a detailed explanation of testing and sporting progression, see Return to Sport After ACL Reconstruction.


Can an ACL Graft tear again?

Yes. A reconstructed ACL can be injured again, although individual risk depends on factors including age, sport, exposure to pivoting activities, rehabilitation and subsequent injuries.


Risk reduction strategies may include:

  • Completing rehabilitation
  • Restoring adequate lower-limb strength
  • Improving jumping and landing mechanics
  • Progressive change-of-direction training
  • Completing sport-specific preparation
  • Continuing injury-prevention exercises
  • Avoiding premature unrestricted return to sport


The ACL in the opposite knee can also be injured, particularly in athletes returning to high-risk sports.


What is Revision ACL Reconstruction?

Revision ACL reconstruction is another operation performed when a previous ACL reconstruction has failed or no longer provides adequate knee stability.


Reasons a revision procedure may be considered include:

  • Traumatic graft rupture
  • Recurrent instability
  • Graft stretching or failure
  • Problems with previous graft position
  • Associated meniscus or cartilage injuries
  • Other structural problems within the knee


Revision surgery can be more complex than a first or primary ACL reconstruction.


Assessment may include review of previous surgery, imaging, graft choice, existing bone tunnels, knee alignment and associated damage.


In some situations, revision reconstruction can be performed in one operation. In others, treatment may need to be staged—for example, where previous bone tunnels require treatment before a new graft can be placed.


Frequently Asked Questions

Is ACL reconstruction always required after an ACL tear?

No. Some people achieve adequate stability and function with rehabilitation alone. Reconstruction may be considered when instability persists, associated injuries influence treatment, or the patient wishes to return to high-demand pivoting activities.


Is ACL reconstruction the same as ACL repair?

No. Reconstruction replaces the damaged ligament with a graft. Repair attempts to preserve and reattach the patient's original ACL tissue. Reconstruction remains the established surgical approach for many ACL tears, although repair techniques may be considered in selected injury patterns.


Will I need crutches after ACL reconstruction?

Crutches are commonly used during early recovery. How long you need them depends on your walking ability, comfort, your surgeon's instructions, and whether you had additional procedures such as meniscus repair.


Will I need a knee brace?

Not every patient requires a brace. Its use depends on the procedure, associated injuries and the surgeon's postoperative protocol.


What happens if ACL reconstruction fails?

A failed graft does not automatically mean further surgery is required. The knee should first be reassessed to determine why the reconstruction failed, whether instability remains and whether revision ACL reconstruction would help the patient achieve their goals.

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