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Woman running with knee injury. Is it possible for my partial ACL tear to heal without surgery?

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If you have suffered a partial ACL injury, you may be wondering what your options are. If your ACL will heal on its own or how long your recovery will be. With complete ACL tears, the recovery options and timelines are well defined. You have a choice between either reconstruction surgery or non-surgical rehabilitation where the ligament is not repaired. With partial ACL tears the options are actually very similar and there are a number of reasons why a person may choose one or the other.

What is a partial ACL tear?

Ligament injuries can be classified into three “grades” of injury with grade 1 being the least severe and grade 3 being the most severe.

Grade 1: The ligament fibres stretch but do not tear [3]

  • Mild swelling and pain
  • No feelings of instability or knee giving out
  • No laxity (excess joint movement) with a normal feeling of resistance when stretched (firm end-feel)

Grade 2: The ligament fibres are partially torn [3]

  • Moderate swelling and pain
  • Knee may feel unstable or give out during activity
  • Some increased joint laxity but still a similar feeling of resistance when stretched (firm end-feel)

Grade 3: The ligament fibres have been completely torn [3]

  • Limited pain and variable amounts of swelling initially, followed by delayed swelling due to joint bleeding 1-2 hours after injury (Haemarthrosis)
  • Feelings of instability and giving out
  • Significantly increased laxity with no feeling of resistance with ligament testing (empty end-feel)

A complete ACL tear would be classified as a grade 3 ligament injury. Partial tears are not as well defined and there is a lot of variability in the severity and definition of a partial ACL tear.[6] For the purposes of this blog we will classify partial ACL injuries as grade 2 ligament injuries; however within that definition there may be people with ACLs that are almost completely torn and some with ACLs that are only slightly torn.

How common are partial ACL tears?

There is lots of research on the number of complete ACL tears each year. You can even determine your risk of complete ACL tears by sport, level of play, and a number of other variables. In the US it is estimated that there are up to 250,000 ACL tears each year.[13] Determining the number of partial ACL injuries is more difficult due to variable definitions and difficulty in diagnosing a partial tear. That being said, we do know that partial ACL injuries are not very common. Research suggests that partial ACL tears make up anywhere from 5-28% of ACL injuries.(11;12) The variability in reporting may be for a number of reasons, such as differing definitions of a partial ACL tear and difficulty diagnosing the extent of the injury.

Will a partial ACL tear heal on its own?

People often think that because the ligament is not completely torn it will heal on its own, but this is typically not the case. The ACL does not heal on its own because it does not have any blood supply to it.[2] For this reason recovery from an ACL tear is very similar to a complete ACL tear.

Picture of a partially torn ACL with about half of the fibres torn. The ACL is made up of 2 parts, the Anteromedial (AM) and posterolateral (PL) bundles, that combine to form one ligament. In this image the AM bundle is torn.
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Image from Sonnery-Cottet, B., & Colombet, P. (2016). Partial tears of the anterior cruciate ligament. Orthopaedics & Traumatology: Surgery & Research, 102(1), S59-S67.

How do I recover from a partial ACL tear?

Before answering this question it is helpful if you know the typical recovery process for a complete ACL tear. A complete ACL tear can be treated either through an ACL reconstruction surgery or non-surgically.[7] Whether someone chooses to have their ACL reconstructed or not depends on many personal factors as well as factors related to the injury.[7] If the person wants to return to activities with jumping, cutting and pivoting, surgery is usually recommended, but if they just want to do straight line activities then non-surgical treatment is a good option also.[7] There is increasing evidence that non-surgical treatment may be an option, even for people that want to participate in sport. Even if a person wants to have surgery, a rehabilitation program of “prehabilitation” is recommended to improve their function and strength before surgery.[7] Another consideration is if there is damage to another structure in the knee as well as their ACL, such as a meniscus or medial collateral ligament (MCL), then surgery is often recommended.[7] Overall, the length of recovery from a complete ACL injury is approximately 9-12 months if you have a reconstruction surgery.[10] Recovery is shorter without surgery (approximately 3 months).[5]

Recovery from a partial ACL injury can also be done through surgery or non-surgical rehabilitation; however which is the best option is less clear as there is more variability with these injuries. If you want to return to sports and an active lifestyle, surgery may be the best option, as with a complete tear. This is because it is common for the remaining ACL to tear if it is not repaired, especially if participating in contact sports or sports with pivoting or people under the age of 20.[9][13] One study estimated that almost 40% of partial ACL tears will result in a complete tear in the future.[9][13] But with surgical reconstruction, there is also a risk of re-injury.[1]

For people with a partial tear that leads to a complete tear, 50% have a meniscus injury also.[9] Injury to other knee structures such as the meniscus is a factor that may indicate that surgery is recommended in partial ACL tears, as in complete tears.[7][12] If the partial tear also resulted in a bone bruise, there is an 80% chance of it progressing to a complete tear.[13] It is also important to consider that the risk of retearing is also going to depend on the extent of the partial tear, meaning if the ACL is 75% torn it is more likely to tear than if it is only 25% torn.

Boys playing soccer. How do I recover from a partial ACL tear?
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Image by Monkey Business Images from Canva.com

The long term outcomes do seem to be slightly better for partial ACL tears as people with partial ACL tears are less likely to have injury to other knee structures, less likely to need surgery, and are more likely to return to the same activities as before the injury than people with a complete ACL tear.[4][8]

The amount of laxity (excessive joint movement) is also a factor. One study recommended that if there was less than 4 mm of increased forward movement of the lower leg on the thigh when testing the ACL, surgery was not recommended; but if it was greater than 4 mm then surgery was recommended.[12] If your knee has very little laxity and does not feel unstable when you move and do your day-to-day activities then non-surgical treatment may be a good option for you.[13]

There are multiple surgical approaches to repair a partially torn ACL, but there is debate over which approach is best.[12] The traditional surgical approach for a partial ACL tear is an ACL reconstruction surgery, as in a complete tear. ACL reconstruction surgery requires the remaining ACL to be cut before reconnecting the entire ligament using a graft (a piece of tissue from another part of the body). Your surgeon may recommend you try a non-surgical rehab and then come back if you end up with a complete tear in the future. The recovery time for a partial ACL tear is similar to that of a complete tear, both for surgical and non-surgical treatment options.

Conclusion

If you have a partial ACL tear, it is unlikely that it will heal on its own. ACL surgery and non-surgical rehab are both reasonable options. There are a number of factors that influence if surgery is indicated such as the amount of knee instability and excess movement, the extent of the tear, if there is a bone bruise, and what activities you want to participate in going forward. The risk of not having a partial tear surgically repaired is that it may lead to a full tear in the future; however, surgery usually requires the ligament to be fully torn anyway. In summary, when deciding how to recover from a partial ACL injury, you must consider both the extent of your injury and your desired activity levels in the future.

Regardless of the extent of your injury and if you have surgery, a progressive rehab program is essential for getting you back to what you love to do and preventing further injury or re-injury. The Curovate mobile app has surgical and non-surgical ACL rehab programs that can guide your rehab and get you back to normal. Find our download links below.

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Other Blogs Related to ACL Injury

References

1. Acl rehabilitation: Re-injury and return to sport tests. Physiopedia. (n.d.).

2. Anterior Cruciate Ligament (ACL) Injuries | Michigan Medicine. (n.d.).

3. Anterior cruciate Ligament (ACL) Injury. Physiopedia. (n.d.).

4. Barrack, R. L., Buckley, S. L., Bruckner, J. D., Kneisl, J. S., & Alexander, A. H. (1990). Partial versus complete acute anterior cruciate ligament tears. The results of nonoperative treatment. The Journal of bone and joint surgery. British volume, 72(4), 622-624.

5. Can an acl tear heal without surgery? Gustavel Orthopedics | Sports Medicine | Orthopedic Surgery. (n.d.).

6. Daniel, D. M., & Fithian, D. C. (1994). Indications for ACL surgery. Arthroscopy: The Journal of Arthroscopic & Related Surgery, 10(4), 434-441.

7. Diermeier, T. A., Rothrauff, B. B., Engebretsen, L., Lynch, A., Svantesson, E., Senorski, E. A. H., ... & Musahl, V. (2021). Treatment after ACL injury: Panther Symposium ACL Treatment Consensus Group. British Journal of Sports Medicine, 55(1), 14-22.

8. Evans, N. A., Chew, H. F., & Stanish, W. D. (2001). The natural history and tailored treatment of ACL injury. The Physician and sportsmedicine, 29(9), 19-34.

9. Fayard, J. M., Sonnery-Cottet, B., Vrgoc, G., O’Loughlin, P., de Mont Marin, G. D., Freychet, B., ... & Thaunat, M. (2019). Incidence and risk factors for a partial anterior cruciate ligament tear progressing to a complete tear after Nonoperative treatment in patients younger than 30 years. Orthopaedic journal of sports medicine, 7(7), 2325967119856624.

10. Mayo Foundation for Medical Education and Research. (2021, March 6). Acl reconstruction. Mayo Clinic.

11. Pujol, N., Colombet, P., Cucurulo, T., Graveleau, N., Hulet, C., Panisset, J. C., ... & Djian, P. (2012). Natural history of partial anterior cruciate ligament tears: a systematic literature review. Orthopaedics & Traumatology: Surgery & Research, 98(8), S160-S164.

12. Sonnery-Cottet, B., & Colombet, P. (2016). Partial tears of the anterior cruciate ligament. Orthopaedics & Traumatology: Surgery & Research, 102(1), S59-S67.

13. Tjoumakaris, F. P., Donegan, D. J., & Sekiya, J. K. (2011). Partial tears of the anterior cruciate ligament: diagnosis and treatment. Am J Orthop (Belle Mead NJ), 40(2), 92-7.