Knee ACL Reconstruction Surgery

Anterior Cruciate Ligament Reconstruction

The anterior cruciate ligament is one of the major stabilizing ligaments in the knee. It is a strong rope like structure located in the centre of the knee running from the femur to the tibia. When this ligament tears unfortunately it doesn't heal and often leads to the feeling of instability in the knee.

ACL reconstruction is a commonly performed surgical procedure and with recent advances in arthroscopic surgery can now be performed with minimal incisions and low complication rates.

History and Examination

Patients often give a classic history of their injury. It usually occurs following a non contact pivot injury to the knee however can also occur during contact sports. Classic features of the history include:

  • Twisting knee injury
  • Heard a pop
  • Felt a clunk
  • Could not play on
  • Knee swelling within 4 hours if injury
  • Severe Pain
  • Knee gives way

As part of the work up, patients require a plain xray and MRI of the knee.

Do I need an ACL reconstruction?

The ACL does not tend to heal itself. It is within the knee joint and the joint fluid prevents healing. A new ligament must be reconstructed using another tendon. If you play pivoting sports or have symptoms of instability in daily life consider ACL reconstruction. I would recommend surgery in most patients who wish to continue participation in sport or physical work.

There are definite benefits to surgery. It provides knee stabilization and prevents further damage to structures inside the knee particularly the meniscus and cartilage surfaces of the femur and tibia.

Timing of Surgery

Timing of surgery varies between patients. It is generally recommended that patients have surgery within 6-8 weeks post injury. You must have regained a full range of motion of the knee joint and most of the swelling must be resolved prior to surgery. Some patients have an injury to the medial collateral ligament (MCL) as well as the ACL tear and require a period of knee bracing pre-operatively to allow the MCL to heal. I do not perform the surgery until stiffness is fully resolved.

Graft Types

Many graft types are available to use. These include:

  • Hamstring tendons
  • Patella Tendon
  • Quads tendon
  • Allograft
  • Artificial graft (LARS)

Most surgeons in Australia perform a 4-strand hamstring graft which is stronger than the native ACL. I prefer to use a 5-strand hamstring graft which allows for larger bone tunnels for the graft and indeed a stronger graft. I also regularly use a middle third patellar tendon graft. The long term results and survival of both these grafts in the literature are similar.

The LARS ligament has received a lot of media publicity following its use in some high profile athletes. Only short-term outcomes were available. There are surprisingly few studies reporting on LARS ligament outcomes. Only short term outcomes are available. We do know that shedding of synthetic debris from this ligament inside the knee can cause synovitis and predispose to early arthritis. It is my preference to not use the LARS ligament for primary ACL reconstruction.

Specific Risks of surgery: are all relatively small

  • Infection
  • Deep Vein Thrombosis
  • Excessive bruising and swelling
  • Joint stiffness
  • Graft Failure 5-10%
  • Numbness
  • Nerve or vessel damage
  • Donor site problems
  • Hardware Problems
  • Residual Pain and swelling


Following surgery the patient will remain in hospital for one night and will have three doses of post operative antibiotics. The majority of patients will not require a brace and will be bearing full weight as tolerated with crutches upon discharge. I advise early involvement with physiotherapy to for swelling control and knee range of motion. As a rough guideline, patients will be on crutches for 2 weeks, jogging in a straight line by 3 months and running with pivoting by 7 months. A return to competitive or contact sport will be 9-12 months.

Physiotherapy is an extremely important part of recovery. The time commitment to this part of the overall treatment is approximately 9-12 months however your physiotherapist will be your guide.

ACL Reconstruction Hamstring Tendon

ACL Reconstruction Patellar Tendon