Australia has one of the highest rates of ACL injuries in the world. New research is emerging about ACL injuries, which challenges traditional beliefs and management.

ACL Injuries and management - Part 1

By Michael Ingle
APA Titled Musculoskeletal Physiotherapist

This blog is the first in a two-part series about ACL injuries. Australia has one of the highest rates of ACL injuries in the world. New research is emerging about ACL injuries, which challenges traditional beliefs and management. Most people in Australia who are diagnosed with an ACL tear undergo surgery soon after the injury.

This is usually based on two assumptions:

Assumption 1: The ACL cannot heal

Assumption 2: Having a torn ACL will render the knee ‘unstable’; if surgery is not undertaken it will limit the ability to return to sport and the knee will be prone to arthritis in the long term.

Can the ACL heal?
People with ACL tears frequently hear that the torn ACL has no potential to heal. However, multiple studies demonstrate that the ACL has the ability to heal in a significant proportion of people (Ihara and Kawano 2017; Costa-Paz et al 2012; van Meer et al 2014; Fujimoto et al 2002). It is proposed that when a ligament is torn, it forms a blood clot in the area which attracts stem cells which morph into the cells that have the ability to lay down new collagen tissue – the stuff that ligaments are made out of (see Ferretti (2020) for more info).

An example of ACL healing, taken from Costa Paz et al (2012) is shown below, where the injured person had a repeat MRI 2 years after the original injury.

ACL soon after injury and after 2 years

Another example below, from Ihara and Kawano (2017) shows a healed ACL in a 28 yo female, managed without surgery. Interestingly, this study of 102 people showed that certain types of tears have a higher chance of healing than others. Further research in this space may enable us to predict who will or won’t heal. We are eagerly awaiting publication of ongoing Australian research in this field.

ACL healing without surgery

Some papers such as this suggest low healing rates, however upon closer review, only 21 of the 1512 patients who sustained an ACL tear in the study (ie 1.4%) were managed without surgery. We therefore don’t know what percentage of this group would have healed with conservative management, when the vast majority were treated with surgery.

How long does the ACL take to heal?
If the ACL is going to heal, like any injury, it is going to heal at different rates for each person. Ihara et al (1994) showed that substantial healing occurs within 3 months of injury. The images above from Ihara and Kawano (2017) suggest that further healing continues over a longer period of time.

Here is an example of an elite athlete, with an ACL tear that healed within 6 weeks.

What does this mean for me if I have an ACL tear?
  • Commence a structured physiotherapy program for at least 3 months – give your ACL the chance to heal without surgery.
  • Reassess the ACL integrity with a follow-up MRI scan after 3 months.
  • Surgery can be performed later if needed, without increased risk of a detrimental outcome (Filbay and Grindem 2019).
Delaying ACL surgery also gives the knee a chance to recover from the original injury, and for the person to regain their muscle strength and movement control. For many, this can be a successful outcome and their knee will ‘hold up’ well during active life.

For part two of our ACL series, please click here  

Kieran Richardson, Specialist Musculoskeletal Physiotherapist, FACP.

Michael Ingle - Brisbane Physiotherapist

Michael is a titled musculoskeletal physiotherapist. Call our clinic on 07 3395 2448 to make an appointment with Michael Ingle.

Costa-Paz, M, Ayerza, M, Tanoira, I, Astoul, J and Muscolo, D (2012). Spontaneous Healing in Complete ACL Ruptures: A Clinical and MRI Study. Clinical Orthopaedics and Related Research, Apr, 470(4), 979-985.
Ferretti, A (2020) To Heal or Not to Heal: The ACL Dilemma. Journal of Orthopaedics and Traumatology, Aug, 21(11).
Filbay, S and Grindem, H (2019). Evidence-Based Recommendations for the Management of Anterior Cruciate Ligament Tears, Best Practice and Research. Clinical Rheumatology, Feb, 33(1), 33-47.
Fujimoto, E, Sumen, Y, Ochi, M and Ikuta, Y (2002). Spontaneous Healing of Acute Anterior Cruciate Ligament (ACL) Injuries – Conservative Treatment Using an Extension Block Soft Brace Without Anterior Stabilization, Archives of Orthopaedic and Trauma Surgery, 122, 212-216.
Ihara, H and Kawano, T (2017). Influence of Age on Healing Capacity of Acute Tears the Anterior Cruciate Ligament Based on Magnetic Resonance Imaging Assessment, Journal of Computer Assisted Tomography, 41(2), 206-211.
Ihara, H, Miwa, M, Takayanagi, K and Nakayama, A (1994). Acute Torn Meniscus Combined with Acute Cruciate Ligament Injury. Second Look Arthroscopy After 3-Month Conservative Treatment. Clinical Orthopaedics and Related Research, Oct (307), 146-154.
Van Meer, B, Oei, E, Bierma-Zeinstra, S, Van Arkel, E, Verhaar, J, Reijman, M and Meuffels, D (2014). Are Magnetic Resonance Imaging Recovery and Laxity Improvement Possible After Anterior Cruciate Ligament Rupture in Nonoperative Treatment?, Arthroscopy: The Journal of Arthroscopic & Related Surgery, Sept, 30(9), 1092-1099.

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