ACL injury and reconstruction

What is it?

The Anterior Cruciate Ligament (ACL) is a tough band of tissue that helps to keep  the knee stable and its main role is to prevent excessive forward movement of the tibia (shin bone) on the femur (thigh bone). It attaches from the tibia up and backwards to bottom of the femur. The ACL can get injured by excessive twisting movements at the knee, hyperextension (where the knee straightens too far) or by excessive knee flexion (where the knee bends too far). This is usually through a non-contact mechanism, however contact injuries account for about 30% of all ACL injuries and more injuries happen in females than males. 

How is it fixed? 

Depending on the extent of the injury, you may or not be offered surgery to reconstruct the damage ACL. Your Doctor and physiotherapist will discuss the best option for you, with you. Factors that will affect this decision depend on age, the amount of damage to your ACL and how active you are. 

Should the decision be made to have the ACL reconstructed, the surgeon will graft a “new” ACL from either your hamstring or gracilis muscle tendon, or your patella tendon at the front of your knee. There is little difference in your rehabilitation outcome with each graft and your surgeon will decide which option is best based on a variety of factors. The surgeon will remove the damaged parts of the original ACL and drill holes in your tibia and femur. Within these holes, the new graft will be placed and secured and will become your new ‘ACL’. 


The typical time for rehabilitation is between 9-12 months. This varies depending on the level of activity you wish to return to and how well you do with rehabilitation. There are different phases of rehabilitation, focused on achieving different outcomes to allow you move onto the next phase. Some people will progress faster/slower than what is described below. A brief description of each phase is listed below. 

Phase I (Pre-operative)

  • Increase leg strength
  • Maintain normal function

Phase II (Immediately Post-operative; Week 1-2)

  • Restore normal knee movement and flexibility (range of movement)
  • Restore normal walking
  • Wean from crutches
  • Reduction of swelling
  • Scar management

Phase IIIa (Strengthening; Week 2-6)

  • Leg muscle strengthening (Closed kinetic chain exercises)
  • Balance improvement
  • Swelling maintenance

Phase IIIb (Strengthening; Week 6-12)

  • Leg Muscle Strengthening (Open kinetic chain exercises)
  • Start cycling and running at low speeds

Phase IV (Preparation for return to sport; Month 3-6) 

  • Non-contact, sport specific drills
  • Jumping, hopping & landing practice

Phase V (Return to sport; Month 6-9)

  • Gradual re-integration back into practice
  • Slowly start introducing contact

Phase VI (Return to competition; Month 9+)

  • Cleared to play competitive games


Beardshaw, A., Penhaul, L., Kennedy, N., Clayton, L. & Wheeldon, N. (2012). ACL Reconstruction physiotherapy advice for patients. URL:

Boden, B. P., Sheehan, F. T., Torg, J. S. & Hewett, T. E. (2010). Non-contact ACL injuries. Mechanisms and Risk Factors. Journal of American Academy of Orthopaedic Surgery, 18 (9): 520-7

Duthon, V. B., Barea, C., Abrassart, S., Fasel, J. H., Fritschy, D. & Menetrey, J. (2006). Anatomy of the Anterior Cruciate Ligament. Knee Surgery in Sports Traumatology and Arthroscopy, 14: 204-13

Eitzen, I., Holm, I. & Risberg, M. I. (2009). Preoperative quadriceps strength is a significant predictor of knee function two years after anterior cruciate ligament reconstruction. British Journal of Sports Medicine; 43: 371-6

Relph, N., Herrington, L. & Tyson, S. (2014). The effects of ACL injury on knee proprioception: A Systematic Review. Physiotherapy, 100: 187-95

Samuelsen, B. T., Webster, K. E., Johnson, N. R., Hewett, T. E. & Krych, A. J. (2017). Hamstring Autograft versus Patellar Tendon Autograft for ACL Reconstruction: Is There a Difference in Graft Failure Rate? A Meta-analysis of 47,613 Patients. Clinical Orthopaedic Related Research, 475 (10): 2459-68.

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