Can a torn ACL truly heal itself?

Written by Dr Sean Leo, a consultant orthopaedic surgeon whose clinical focus is the knee, sports injuries and the lower limb.

Last updated: 9 October 2026.

Emerging evidence suggests that some acute anterior cruciate ligament (ACL) tears may show healing, but the evidence so far is limited and conflicting. A randomised comparison is registered, so definitive conclusions are not yet available. That is not the same as saying a torn ACL heals itself, and it is not a reason to put off an assessment.

What does the emerging evidence show?

• The main published findings come from a group of patients followed without a control group assigned by chance (a case series). ^[1]
• Seeing continuity on a scan is not the same as having a normal ligament or a stable knee.

More on the original healing study

The original study (Filbay et al., 2023) followed 80 consecutive patients with no comparison group. ^[1] An MRI scan (a detailed scan of the knee) showed evidence of ACL healing at three months in 72 of 80 participants (90%). ^[1] Continuity on a scan is not the same as normal ligament structure, stable function, return to sport or freedom from reinjury. 11 participants (14%) re-injured their ACL, on average about 10 months later (range 5 to 18 months). ^[1] The authors noted the possibility of selection bias and called for longer follow-up and clinical trials. ^[1]

What does this page cover?

• What does the emerging evidence show?
• What is the Cross Bracing Protocol?
• Is Cross Bracing right for everyone?
• What role does the ACL play in knee stability?
• How does healing evidence relate to surgery?
• When should a knee injury be checked urgently?
• What should I do next?

What is the Cross Bracing Protocol?

Cross Bracing was developed to bring the torn ends of the ACL closer together during early healing. It is a brace protocol, not a cast.

• The evidence for it so far is limited and conflicting.
• A randomised comparison is registered, so definitive comparative conclusions are not yet available.

More on the original protocol

In the original report, 80 consecutive patients who presented soon after the injury were managed with a supervised bracing protocol, together with supervised rehabilitation. The authors noted that the protocol was adapted over time, so it is not a fixed schedule. ^[1]

Is Cross Bracing right for everyone?

No single protocol suits every knee. Cross Bracing asks a great deal of the person undertaking it, and its risks and inconveniences are not trivial. It should be supervised by appropriately trained clinicians and physiotherapists. It should not be copied from a webpage.

• Weeks with the knee held in a brace.
• Crutches for the first weeks while the knee is held in the brace.
• Possible disruption to work, mobility and caregiving arrangements. The extent varies from person to person.
• Loss of motion and muscle capacity that must be recovered afterwards.
• The original report also recorded deep-vein thrombosis (DVT, a blood clot in a leg vein) in two patients, which led the treating group to add preventive measures. ^[1] Individual clot risk, safe mobility and prevention need clinician oversight, and no anticoagulant dose is given here.

More on a later comparison with surgery

A later prospective controlled cohort study (Porter and Shadbolt, 2026) of 80 active people aged 16 to 40 who intended to return to pivoting sport compared Cross Bracing with surgical stabilisation at two years. ^[2] Recurrent instability was recorded in 70% of the Cross Bracing group (40 people) and 2.5% of the surgical group (40 people), and a medial meniscal tear (a tear of the cartilage cushion on the inner side of the knee) in 62% and 2.5%. ^[2] Treatment was chosen rather than randomised, and all the patients came from one private practice, so the comparison may be affected by who chose each option. ^[2]

What role does the ACL play in knee stability?

The ACL is one of the major ligaments within the knee. It contributes to control of forward and rotational movement of the shin bone relative to the thigh bone, particularly during tasks such as landing, cutting and pivoting.

• When the ACL is torn, some knees remain functionally stable for daily activities, while others repeatedly give way during sport, work or ordinary turning movements.

More on how much the ACL restrains the knee

In cadaver studies, the ACL provided about 82-89% of the restraint to the shin bone moving forward at 30° of knee bend, decreasing to about 74-85% at 90°. ^[6] Cadaver figures describe laboratory measurements, not a living knee.

How does healing evidence relate to surgery?

Evidence about healing does not remove the reasons surgery is sometimes considered. Some people can regain useful function with structured rehabilitation and changes to activity, while others continue to have episodes of giving way or need stability for work or sports involving cutting and pivoting.

• Associated meniscal, cartilage or other ligament injuries may also alter the decision.
• A clinical assessment is needed, because evidence from newly injured patients should not be applied automatically to people with longstanding symptomatic instability.
• Reconstruction is considered for persistent functional instability, recurrent giving way, a goal of returning to high-demand cutting or pivoting activity, or associated injuries whose management changes the balance.
• This is not the same as saying that every athlete needs surgery or that age alone determines treatment.

More on how studies compare rehabilitation and surgery

In the KANON trial (a randomised trial, in which people are assigned to a treatment by chance) of young active adults with a first-time acute ACL tear, early reconstruction did not provide better patient-reported or radiographic outcomes at five years than rehabilitation with optional delayed reconstruction. ^[3] About half (51%) of those assigned to the optional delayed reconstruction group did go on to have the operation within five years. ^[3] This trial compared management strategies. It is a different study from the Cross Bracing cohort described above.

As summarised by Brophy and Lowry (2023), the American Academy of Orthopaedic Surgeons (AAOS) clinical practice guideline “Management of Anterior Cruciate Ligament Injuries” (2022) gives a strong recommendation: “When surgical treatment is indicated for an acute isolated ACL tear, early reconstruction is preferred because the risk of additional cartilage and meniscal injury starts to increase within 3 months.” ^[5] The published guideline summary notes that this applies most to younger and more active patients and is less applicable to older and less active patients, who may do well with non-surgical treatment. ^[5]

ACL reconstruction can often be done as day surgery. People with other medical conditions, or who need closer monitoring, may be advised to stay in hospital.

When should a knee injury be checked urgently?

What should I do next?

If you are wondering whether an ACL tear could heal, an assessment is the sensible next step. It brings together what happened, an examination and any tests that help, so that you and your clinician can decide what to do next. An appointment supports an informed decision. It is not a commitment to surgery.

• Read how the treatment options compare, including rehabilitation-led care and reconstruction, on the ACL reconstruction surgery page.
• Looking at repair rather than healing? See is ACL repair viable as a method of treating ACL injury.
• Browse the Knee Hub for other knee problems.
• Read about ACL tear symptoms.
• Read about who is suitable for ACL repair.
• Read about tips for recovering after ACL surgery.
• Read more about Dr Sean Leo, the orthopaedic surgeon who wrote this page.

References

1. Filbay SR, Dowsett M, Chaker Jomaa M, Rooney J, Sabharwal R, Lucas P, et al. Healing of acute anterior cruciate ligament rupture on MRI and outcomes following non-surgical management with the Cross Bracing Protocol. Br J Sports Med. 2023;57(23):1490-1497. doi:10.1136/bjsports-2023-106931. PMID:37316199. PMCID:PMC10715498. PubMed: https://pubmed.ncbi.nlm.nih.gov/37316199/
2. Porter MD, Shadbolt B. Cross Bracing Protocol for Anterior Cruciate Ligament (ACL) Rupture Has Unacceptably High Failure Rate Relative to Surgical Stabilization: A 2-year Controlled Cohort Study. Clin J Sport Med. 2026;36(4):444-450. doi:10.1097/JSM.0000000000001416. PMID:41622530. PubMed: https://pubmed.ncbi.nlm.nih.gov/41622530/
3. Frobell RB, Roos HP, Roos EM, Roemer FW, Ranstam J, Lohmander LS. Treatment for acute anterior cruciate ligament tear: five year outcome of randomised trial. BMJ. 2013;346:f232. doi:10.1136/bmj.f232. PMID:23349407. PubMed: https://pubmed.ncbi.nlm.nih.gov/23349407/
4. American Academy of Orthopaedic Surgeons. Management of Anterior Cruciate Ligament Injuries: Evidence-Based Clinical Practice Guideline. Rosemont (IL): AAOS; published 22 August 2022 (replacing the 2014 edition). Available from: https://www.aaos.org/aclcpg
5. Brophy RH, Lowry KJ. American Academy of Orthopaedic Surgeons Clinical Practice Guideline Summary: Management of Anterior Cruciate Ligament Injuries. J Am Acad Orthop Surg. 2023;31(11):531-537. doi:10.5435/JAAOS-D-22-01020. PMID:36727995. PMCID:PMC10168113.
6. Patinharayil PG. Biomechanics of ACL. J Orthop. 2017;14(4):A1-A3. doi:10.1016/j.jor.2017.10.002. PMID:29200708. PMCID:PMC5699912. (Editorial summarising earlier biomechanics work.)