Can the ACL heal? The Cross Bracing Protocol: everything you need to know explained to physicians, physiotherapists and patients

If you are a physician or physiotherapist specialized in knee and anterior cruciate ligament (ACL) care, you are likely aware of Stephany Filbay's publication in June 2023 regarding the potential for ACL healing through a bracing protocol: the Cross Bracing Protocol (CBP). Even if you are a patient who has experienced this injury and encountered numerous social media posts questioning the possibility of ACL healing, encouraging you to read further.

In the months following this publication, there has been extensive discussion, commentary, analysis, doubt, and even judgment of its content. Twitter threads and Instagram reels have provided minute-long analyses of this information. Therefore, if you wish to delve deeper, today we present, in a format that will take a bit more of your time, a detailed analysis to provide a comprehensive perspective on this publication. This will enable you to form your own opinion after gaining an in-depth understanding.

Therefore, today we will unfold its story, provide context, explain the research and its findings, and discuss the uncertainties and possibilities in the present and future.


Let's go back to the Stone Age. No, there were no surgeries or orthoses back then, but what is certain is that there were cavemen and cavewomen who also tore their ACLs while hunting mammoths or descending rocks in search of gathering areas. Their knees would swell, hurt, and they would struggle to walk. And what would they do when this happened? In such conditions, it is highly likely that they would retreat to their cave, resting with their knee immobile for a period to facilitate healing before resuming their activities.

This hypothesis, looking at anthropology and nature, didn't occur to Filbay but to two Australian orthopedic surgeons: Mervyn Cross and his son Tom. Mervyn senior, a former rugby player turned doctor, paid special attention during his student days back in 1970 to the anatomy of the ACL. This interest led to, when he started performing surgeries, postoperatively keeping his patients with the knee bent at 90º, knowing that this position would subject the graft to less stress. As surgical materials and techniques advanced, Mervyn abandoned this practice in favor of early mobilization.

It wasn't until 2014 that destiny, as in everything that has to be, intervened. The already retired Mervyn Cross was in rehabilitation as a patient after undergoing knee prosthesis surgery when one afternoon he coincided with Emma, the daughter of the clinic's receptionist. At 19, Emma had torn her ACL playing netball and was in a sea of tears out of fear of the operation. That was when Mervyn spoke with his doctor, who happened to be his son Tom, and with that premise still in his head from the '70s, they decided to place a brace on Emma at 90º flexion for 4 weeks. And, after that time, they confirmed that the ACL had healed.

As a result of this case, from that year until 2018, Mervyn and Tom Cross tried this intervention on 4 more patients, obtaining the same successful result. The fifth was Matt Dowsett, their own grandson and son, who tore his ACL playing rugby while studying medicine following the family saga.

If you were thinking that the CBP had the word 'Cross' in it for fashion, due to CrossFit or Cross Training, or because of Cross Education, well, for now, you know it's not for that reason, but rather named after the doctors Mervyn and Tom Cross. Matt Dowsett later joined the research part and is the second author of Filbay's publication


In the year 2020, Tom Cross presented the results of the first 16 patients treated with this protocol at the Sports Medicine Conference in Australia, convinced by the outcomes that it deserved to be formally studied. It was then that he was introduced to physiotherapist and researcher Stephany Filbay from the University of Melbourne.

Filbay had published the KANON trial in 2017, a pioneering publication that analyzed outcomes in patients with ACL tears randomly assigned to either rehabilitation-only or reconstructive surgery. We can imagine it was an instant match.

It was at this point that, assembling a team of orthopedic surgeons, physiotherapists, and radiologists, Filbay initiated the CBP research, using patients treated between 2016 and 2021 as the study sample.

In November 2022, we were following the Sports Medicine Australian Congress on social media, and we saw Filbay announce, "We've been working, and something important is coming." In it, she discussed the research that had already been conducted and was pending publication about a protocol to promote the healing of the ACL.

And in January 2023, she released a teaser: the analysis conducted on the results of the KANON study group, the same one from the 2017 publication but re-evaluated over the long term. It was observed that in the group treated with a conservative approach, 45% had eventually undergone surgery, and in the remaining 55% that had avoided surgery, undergoing MRI at 2 and 5 years revealed, surprisingly, that approximately one in every two had healed their ACL.

And not only that, because in the end, an image is just an image, but measured through scales, patients in this group who showed healing had better functional outcomes than those who hadn't healed, and even better than those who had undergone early or late surgery.

That is, Filbay was showing us that, despite the long-standing belief that the ACL had no healing capacity despite having vascularization, it indeed could heal. This marked the beginning of a potential paradigm shift.

After this study, we all anxiously awaited the publication of the CPB article until it arrived in June 2023. And this is when things got a bit chaotic on social media:


Fundamental Principles of the Protocol

When I studied Physiotherapy, I was convinced that my job would involve doing very complicated things—things that seemed so complex that I believed I wouldn't be able to do them and, therefore, never fully interested me, assuming I would be a basic professional. Years later, it turns out that those complicated things were not as true as I thought. By then, I had already understood that being basic was indeed my job: as basic as knowing how to promote biology and not believing I could perform magic on it.

That's why, when following Filbay's presentation at another conference explaining the protocol, I was amazed when I read that she based it on "The 3 Orthopaedic principles":

  1. Inflammatory Model: Ligaments heal! It explained the phases of inflammation—inflammatory, proliferative, and maturation phases—relating them to the histology of ligament healing. This was something explained in the first year of university but not taught how to apply it to an ankle sprain because you would fix it by adjusting the fibula. Based on this principle, it is decided that the duration of this protocol will be 12 weeks to reach the maturation phase. Patients will be advised not to take anti-inflammatories to avoid interrupting this process, and they may choose analgesics to manage pain.
  2. Blood Supply: Drawing an analogy with a sausage, it explained how the skin was the synovial membrane of the ACL, while the meat represented the ligament. It likened this skin to a butterfly chrysalis, facilitating blood supply to enable healing.
  3. Anatomic Reduction: Comparing it to the treatment of a fracture, where it is understood that the edges need to be aligned for callus formation. This fundamental basic principle is applied in ankle sprain treatment, but at a certain point, we transition from using casts for offloading for a month to using nothing at all because excessive immobilization is detrimental. The shift from experiencing the effects of disproportionate immobilization to the failure of healing due to the lack of any form of restraint on the other end occurred. An ankle sprain, before any magical technique, heals with that functional bandage we stopped using. Therefore, to heal the ACL, it is proposed that some form of reduction also needs to be performed.

Paradoxical that something as revolutionary as the CPB, led by a physician and a physiotherapist, is grounded in basic principles. It is a thought-provoking fact, prompting reflection on whether healthcare professionals have at some point deviated from the path and now find themselves needing to return home.

The Protocol

The complete protocol can be found in the appendix of the study or translated into Spanish on the Knee Spain website. It is based on the use of an adjustable orthosis for 12 weeks. During the first 4 weeks, it is set to a 90º angle (as, according to the studies it is based on, the least tension on the ACL occurs between 90º and 135º, with 90º chosen as the position of least discomfort for the patient within this range). The amplitude and weight-bearing load are then gradually increased over the following weeks according to the following progression:

  • Week 4: 90º NBW (non-weight bearing)
  • Week 5: 60º-90º NBW
  • Week 6: 45º-90º PWB (partial weight bearing)
  • Week 7: 30º-Full FLEX PWB
  • Week 8: 20º-Full FLEX PWB
  • Week 9: 10º-Full FLEX PWB
  • Week 10: 0º-Full FLEX FWB (full weight bearing)
  • Week 12: MRI and orthosis removal FWB

Complete flexion would be achieved in week 7, and full extension in week 10. Regarding weight-bearing, during the first 5 weeks, the patient undergoes total offloading, transitioning to partial in the 6th week, and achieving full weight-bearing in the 10th week when complete extension is allowed.

But the protocol is much more than a sequence of amplitudes within an orthosis and a progression of weight-bearing. If you look at the table, the first column indicates the biological time, and the second indicates the orthosis progression. In a country like Spain, where the consideration towards Physiotherapy is often seen as a complement to medicine rather than an essential discipline in addressing these types of injuries, many might understand the protocol as merely the first two columns, with the patient lying down at home, taking the opportunity to watch Netflix.

However, if we adopt the Australian approach, the protocol includes a third and fourth column indicating the goals and physiotherapy treatment, including items such as exercise to preserve local and overall body strength or cardiovascular exercise. These are very important items: first, in achieving results, because in a patient where circulation and oxygenation are not activated, can we expect the same healing? And second, in avoiding the establishment of side effects.

And this should already make us understand a very important idea to keep in mind:

The CPB is not just a medical protocol, it is a protocol of Medicine and Physiotherapy.

The Results of the Research

After applying the protocol for 12 weeks, it is at the conclusion of this period that a new MRI is performed, and its image is re-evaluated using the ACLOAS scale.

And the results show the following:

In other words, considering ACLOAS grades 0 to 2 as indicating a healed ligament, 90% of patients achieved this outcome. However, the research doesn't conclude there; a new MRI is repeated at 6 months. During this time, 4 patients with ACLOAS 1 progressed to ACLOAS 0, indicating a completely healed ACL without even the thickening of a scar. Although an image is just an image, the patients with ACLOAS 1 also showed higher values in functionality and quality of life scales compared to the other groups. This was evident even in the Lachman and Pivot Shift stability tests.

The lives of the patients continued beyond those 6 months. From the ACLOAS 1 group, 92% returned to sports compared to 64% from ACLOAS 2 and 3. Between 5 and 18 months, 11 patients (14%) experienced a re-injury: 4 with ACLOAS 1 and 7 with ACLOAS 2 and 3. Both percentages, Return To Play and re-injury, are considered quite similar and even favorable compared to those of patients undergoing surgery. As a curious note, one of these patients who experienced a re-injury underwent the CPB again, achieving an ACLOAS 1.

And if we compare the data with the results of the Kanon group's 2017 study (where, without a specific approach like this, a 53.33% healing rate was achieved), in this study with the application of CPB, the percentage rises to 90%:


This research brings significant biological advantages of CPB, such as the ability to maintain your native ligament and, therefore, its neurological function as a proprioceptive sensor, while also avoiding surgery and the iatrogenic damages it implies. Additionally, it helps mitigate the psychological and social impact, including economic costs. Therefore, the results deserve further investigation with greater precision, considering the limitations of this publication.

When interpreting this research, it's crucial to consider that it's a single study with a small sample size and a case study design, not a clinical trial with a control group, where not all patients received identical interventions. For example, 14 patients received a platelet-rich plasma (PRP) injection. The first 4 patients, whom Tom Cross treated with CPB before organizing the study, had a different orthosis periodization. Also, the criteria for Return to Play might be limited. In fact, the study's limitations section explains that, rather than a regulated investigation, this publication is a data collection from clinical practice. Therefore, the data, promising as they are, call for further structured research to obtain more reliable information.

That's why the idea of implementing CPB, for instance, in a private practice in Spain or Japan outside of a research context might seem premature at this point, lacking guarantees or sufficient information to offer patients for informed decision-making.

Filbay herself is already continuing this line of research by bringing it to the United States, so we can expect new information in the medium term. It is anticipated that further exploration will focus not only on the degree of healing that can be achieved as the first challenge but also on other items such as:

  • If healed is equivalent to competent: which is the main focus. In other words, if what is seen in the image translates to the ligament functionally containing the excess joint laxity. In the study, this was measured through the Lachman and Pivot Shift orthopedic tests by non-blinded examiners. Therefore, the study's limitations indicate the need for improvement with future measurements using an arthrometer, a device that can objectively measure this anterior drawer laxity.
  • For what type of patients may it be more indicated according to the type of injury: that 93% of ACLOAS 2 had a femoral avulsion of the ACL at the beginning, compared to 13% of those who achieved ACLOAS 1, may lead us to understand that certain ACL injuries may be more prone to healing than others based on their structural characteristics. Verifying and defining which, by classifying injuries according to this structural typology, can explain why some patients, for example, may have been able to heal them spontaneously. Understanding them better to know which others would need assistance from CPB, refining the profile of the "Healer" or "Responder" patient to target them, and, above all, hypothetically avoiding attempts in those likely to fail due to displaced ends or femoral avulsions, who may need to go directly to conservative or surgical options, stands as another of the main objectives of new studies. And in this regard, 3D MRI will have much to contribute.
  • Timeframes: from 3 to 6 months, 4 patients with ACLOAS 1 had progressed to ACLOAS 0. Future research could continue by studying the healing times, helping us understand the process and duration of the phases, to establish the exact times that achieve the most optimal results.
  • Failure rate: although the Return To Play and re-injury rates in this sample are similar to those of the surgical option, we are comparing a sample of 80 patients against thousands studied in decades of surgical treatment research. Therefore, future studies that expand the sample size and duration can provide more information on these items, as well as patient satisfaction and the incidence of knee osteoarthritis.

But none of this should deny the importance of the significant contribution that this publication has made, which is not even the content of the protocol itself but demonstrating that the ACL could have the ability to heal like other tissues. Moreover, if we compare it with Filbay's previous article, a protocol restricting mobility in the acute phase enhances the possibility of this healing process occurring. Let no one deny that.


It is said that the transmission of science to daily practice takes an average of about 17 years. We do not know if this time will be reduced with social media, but what we do know is that professionals use them to share information like that from this study. And often in extremes.

The Admirers

On one hand, much content has been shared by physiotherapists explaining in reels that the ACL can heal, leaving that idea to the viewer after a minute, even without all that has been explained so far.

A few weeks ago, a physiotherapist colleague from Mexico, a football player, and a participant in a training program, wrote to tell me her case: after an ACL rupture, a conservative option was chosen. She told me how, when she returned to football, she thought, thanks to Filbay's article, that maybe her ACL had healed. At 6 months, she tore both menisci. If this player, who was not only a patient but also a physiotherapist, had such an idea, I am very concerned about what a common patient might be thinking.

If you are a patient with an ACL injury, you will now understand that, although this information is promising, it is not something that, once proven to be possible, means it will happen spontaneously in your case. Nor does it mean that we could offer you guarantees, given that only one study has been conducted, that the CPB will be positive in your case.

The Detractors

On the other hand, the opinion of other physiotherapist and medical colleagues has followed the line of judgment, with statements such as:

  • "I don't understand why at 90º": this information is, as we have mentioned, explained and referenced in the same study. It is necessary to read it.
  • "It is not viable because it will definitely cause knee flexion stiffness": my favorite heard from many experts. Personally, I do not have an opinion if I read the study data: only 14% of patients developed flexion stiffness of -5º to -15º at 4 weeks, which is when the orthosis is locked at 0º, and it resolved in the following 3 weeks. If we read the study carefully, it is not about 12 weeks of immobilization, as many speak in general terms, but in the 5th week, the extension begins to increase, up to complete mobility in both directions, which is achieved in the 10th week. Therefore, this opinion may not be viable... unless instead of following this protocol Australian-style, supervised by physiotherapy from the beginning, with exercises to ensure these ranges of mobility, progressing the weight-bearing, preserving strength, and including cardiovascular exercise, we do it the Spanish way: 3 months on the couch munching Donettes. Or if anything, go to the physiotherapist every day for magnetotherapy. Filbay is a physiotherapist with a doctorate. Perhaps she took this item into account without us giving our opinion after reading it on Instagram. Again, it is necessary to read the study to be able to comment on it.
  • "It may fail, and then you have to have surgery": of course, obviously having been injured once does not make you immune to it happening again, as also happens when you opt for the surgical option. Hence it should be a personal decision based on the risk/benefit assessment of each individual and their situation.
  • "Surgeons won't like it because they won't have surgeries": "surgeons not as happy as physios" has been heard a lot. Surgeons are, first of all, doctors. Therefore, their goal is to help the patient recover with the best results, whatever the necessary intervention. The role of the doctor in the CPB is also Traumatology, and, in the future, it may be the best if results are proven.
  • "Few patients will endure that for three months": my second favorite behind the flexion one. And with this statement, we eliminate the option for those who can, want to, or cannot but want to so much that they themselves weigh the risk-benefit before one of us takes away the option by choosing for them. It is true that, with a high probability, this option will not be viable for Paco, the truck driver I attend to at the occupational health clinic. Due to his social environment, he probably cannot risk being on sick leave for longer with the truck stopped. Or he may live alone and not have anyone to help him commit to respecting the orthosis while managing his daily life. But, however, there are people who live very well, even if we are neither you nor me, and can afford it. Or, simply, it is their preference, and they will see how they have to organize their own lives before we do it for them. It is the case of some patients in the sample who have shared their testimonies on social media, and I highly recommend reading if we want to learn from their experience. One of them is Steven Duhig, who has been interviewed by the JOSPT to tell his story: "Why destroy my knee muscle to fix my knee?" (because let's not forget that many patients think that the surgical approach will repair the damaged ACL, as if it were sewn together with a thread, and not that what is done is to reconstruct it with another donor tissue that will be damaged, that will not have proprioceptive function, that will be tunneled, that will cause a spill, etc). A story of proactivity in which he decided that he did not see sense in subjecting the knee to the iatrogenic damages of the operation when this option existed with which he was successful. He also says that it was not a bed of roses, but above all, it was his decision: where do we remember the psychosocial model and shared decision-making here? And his successful result. Another patient was Meike van Haeringen, a hockey player who, after having operated years ago for the same injury in the other knee, wanted to opt for this alternative. And by the way, not twelve, but after surgery, you will be disabled and needing help for a minimum of weeks anyway. Could it be seen as prolonging a postoperative phase?

The study mentions that some patients opted for the CPB because, as they had an associated medial collateral ligament (MCL) injury, they already had to wear a supportive brace for 4 weeks anyway, and it would not make a big difference for them. In Spain, where MCL sprain is perhaps the most underrated knee injury, and the treatment is usually normal life without sports and anti-inflammatories (some patients come to Rehabilitation with a Tubigrip as a knee brace, a dressing bandage that provides less support than tight jeans), it is also challenging for us to understand that bracing or wearing a brace is a more common and necessary practice than what we see in our daily practice.

One of the few well-founded opinions we have is from Forelli, published in the IJSPT, which could be summarized in one word: caution. Also, keep in mind that we still need to know whether a "healed" ligament is the same as a "competent" one, given that, as Filbay herself also comments, this measurement of laxity was not the most accurate.


The published study on CPB opens a potential window to a new way of approaching ACL injuries: favoring its healing in the acute phase and adding itself as a third therapeutic option to the existing two, surgical and conservative approaches. It becomes a prior option to these two.

But the reality is that this study was not the first to show us this possibility: the first publications on ACL healing date back to the 90s, mainly from Asian research groups. Ihara in 1996 showed a 74% healing rate with an intervention using a brace without mobility restriction, the same percentage that Fujimoto in 2002 showed, although with laxity. These studies already indicated the influence of certain factors, such as minimum tibial slope or maintaining the femoral insertion, as positive predictors of the possibility of healing.

Since then, publications on this topic have continued, many of them isolated cases, such as Costa-Paz in 2012 showing 10 subjects with complete healing. But even in 2023, there have been more publications on the same theme, perhaps overshadowed by Filbay's. One from Previ (Italy) with a series of 6 cases. Another from Razi (Iran) on cases of spontaneous healing in their study analyzing the approach to patients with combined ACL and MCL injuries. And another, the most significant, from Blanke (Germany), with a study of 381 patients where, in the intervention group, 6 weeks of braces without mobility or weight-bearing restrictions were applied, followed by Lachman and Pivot Shift tests, and then directly to arthroscopy. In this study, they found a 14% of patients with healing, in whom a conservative approach was continued, while the rest underwent surgical reconstruction.

As mentioned earlier about Filbay's study, it has a small sample size and an improvable methodology; therefore, we cannot draw hasty conclusions. But personally, I consider that this approach has great potential. First, because nearly three decades of studies have shown that it is possible, without further refining the necessary intervention to increase these percentages and bring it to its maximum effectiveness, as has been done with surgical techniques. Additionally, some ideas came to mind when analyzing this study:

  • The reduction of mobility with orthosis in the acute phase to promote healing has been used for decades in the Posterior Cruciate Ligament (PCL): PCL injuries are classified as grade I (elongation with minimal drawer), grade II (elongation with moderate drawer), and grade III (rupture with severe drawer), and in all cases, an orthosis is applied. It's not just any orthosis, but a specific one that, through the support shown in the image, reduces the posterior drawer of the tibia to apply the reduction principle to this ligament. If you are a physiotherapist in Spain, you may have never seen it. I myself, in all my practice with knee patients, have seen it in only one case and at the suggestion of the patient. But in the United States and the Netherlands, it is a common practice in what is sometimes another underestimated knee injury in Spain, where we have been recommending the conservative option by default for decades when this option is considered, due to the same defect, inadequate in the ACL. This orthosis is placed in grades I and II with the aim of promoting healing, and in grade III because, until the operation, containment is necessary to avoid damaging the vasculonervous plexus. Moreover, as stated by some orthopedic surgeons, "because the image fails." That is, sometimes a grade III appears and it is a I or II because healing was achieved with the orthosis. After reading the article, I wondered "if the image really fails" or if we have been applying a CPB "LCP version" for years without investigating it. And if this approach is applied to the PCL, would it be so groundbreaking to apply it to the ACL? I also wonder if the use of an orthosis like this but an ACL version, with support applied directly to the anteroproximal face of the tibia that reduces the anterior drawer, could make a difference in effectiveness. Investigating this question, I was excited to find that this question was already asked by the orthopedic surgeon Matthias Jacobi, from Switzerland, between 2003 and 2009 (no less than 20 years before the publication of the CPB). During this period, he conducted research applying an ACL Brace, a version of an orthosis designed to reduce the anterior drawer, where, after 4 months of application without limitation of mobility or weight-bearing, he already achieved a result of 55% of cases with healing of the ACL.

  • Aponeurotic surgery: In late 2021, a tweet from footballer Spanish Priscila Borja sparked controversy. After suffering an ACL tear, she had sought the services of a doctor in Madrid who had performed aponeurotic surgery, a non-invasive manual therapy that, she explained, "affected the connective tissue to induce healing of the ACL." Those familiar with the 2017 KANON group study by Filbay commented upon reading the tweet that neither this doctor nor the player were likely aware of the data presented in the study, and that healing was not associated with such intervention. Last year, I documented the medical history of a new patient who had undergone ACL surgery for the second time. In her extensive history, she mentioned that before the first surgery, she had consulted a doctor in Madrid, recommended by a renowned sports traumatologist, to undergo treatment to see if her ACL would heal with a manual technique on connective tissue. She referred to the same doctor, but in her case, it had not worked. Through this patient, I learned that in addition to Spanish traumatologists referring patients to such questionable and non-rigorous interventions, the price per session was 150 euros. And a total cost of 3000 euros. I wonder if, in the "success stories" that this doctor did achieve, which were the ones that brought patients like these to her clinic through word of mouth, they might again have more to do with the potential of the ACL to heal, as stated in the 2017 study and now also in the 2023 study by Filbay, rather than with any manual therapy effect on aponeurotic tissue.

  • But above all, because this reinforces something I often think about after a few years of experience, which is that healthcare professionals have forgotten about nature in favor of our interventionism. In history, we reached a point where we believed that we were curing the body, instead of understanding that we were providing the best pathways for it to heal itself. Acting as intermediaries rather than protagonists. And that's how we have continued to teach it in university schools, just like when I was a student. The body always has a way, which is why I don't find it rebellious that we are starting to be taught with more emphasis on how to help the ACL execute its own. Actually, quite the opposite, something I strongly believe in and will continue to closely follow its research.

I also consider its possible application in partial tears: if PRP, and generally other even less restrictive interventions, have achieved healing in complete tears, how effective could it be when there is already partial continuity? Similar to what is done in a fibrillar tear or a partial tear of an ankle ligament. As with these injuries, could this approach become the default for this type of tear, and could we have been applying it for years?

I also wonder if its application could have even more potential in children. When an ACL injury occurs during the growth stage, there is a particularity: the state of the growth plates. Since they are not closed, performing surgery cannot involve drilling the tunnel in the classic and necessary direction, as damaging this structure would pose a high risk of altering the normal growth of the tibia and femur, leading to limb length discrepancy with serious consequences. Therefore, there are modified surgical techniques for children where either the tunnel is made horizontal, even at the cost of losing vector efficacy, or tunnel-less techniques are performed, which may have a slower integration and be jeopardized by the child's own growth. It's not surprising that the surgical approach in children usually has a higher long-term recurrence rate. So, if CPB has shown potential in adults, what would it be like in children, whose tissue quality and metabolism are already more favorable for healing? In a context where we need to provide better solutions and possibly even avoid surgery at an early age and its impact.

Therefore, I am sure to closely follow the continuation of CPB research in the future. However, I believe that a dilemma arises in the present that may surface in clinical practice regarding the question we posed earlier: should we start performing it on patients in those specific clinics in Spain or Japan? We mentioned that it might seem premature at the moment, without having guarantees or sufficient information to explain and assist patients in their decision-making. And that's true. But what if we consider the following?

  • If applied correctly, and correct means correct, that is, with medical supervision that includes thromboembolism prophylaxis and physiotherapy to ensure the implementation of an exact plan, the worst outcome of having tried it would be delaying either the conservative or surgical approach by three months, if they are subsequently deemed necessary.
  • Many orthopedic surgeries also lack strong evidence supporting their use, unlike CPB, and come with significant risks of secondary damage or complications, in addition to a higher economic cost.
  • There are patients who wish to access this treatment. In Australia, outside of the research, there have already been 500 cases, and Filbay has received over 100 emails from people abroad who want to undergo it. If they are adequately informed about the limitations of the research and still wish to proceed, in a secure manner and in alignment with the mentioned correct implementation, should they be granted access to it?

As professionals driven by science, we should wait for more evidence before promoting this type of approach. However, while awaiting additional evidence and ensuring that the patient is provided with real and comprehensive information, I personally believe there are no compelling reasons to contraindicate it. Therefore, it is feasible for a patient in Spain to undergo CPB if that is their wish. Of course, they should be informed of everything explained in this article and make their own choice, evaluating their risk/benefit situation within their personal circumstances. As we explained, when done correctly, it does not involve risks, and its only drawback is delaying surgery or the start of a conservative approach.

And again, correct is correct. A student in another training session asked me if I would start CPB in my patients. I explained very explicitly that I cannot make this decision, firstly because it is the patient's decision, especially in the current context, and secondly because it should also be weighed by a physician. Similarly, I understand that if a physician asks this same question to a colleague, they will recognize that they cannot apply this protocol as a simple restriction of mobility for 12 weeks without the supervision of a physiotherapist ensuring that CPB is executed as described.

Are these healthcare professionals and patients in Australia guided by evidence? With the heading of the image on the left, Stephany Filbay began her presentation last week at a conference held in Melbourne, explaining, in addition to the arguments already presented, how the classic decision between conservative or surgical approaches is not being made based on evidence. Premises such as "if you don't have surgery, you'll have more arthritis" or "with surgery, you'll have better long-term results" are not supported by evidence. Nothing has been proven and then done, and with minimal demonstrated evidence to initiate these interventions, Filbay explained the current clinical practice with CPB in Australia and the steps they are taking in ongoing research.

I myself believe that if I were affected by an ACL tear right now, I would opt for this approach. My social situation allows for it; I would need a doctor for the assessment of the injury and its structural classification, as well as for thromboembolism prevention. I would also require a specialized physiotherapist to follow the protocol, which, of course, would be very accessible in my own case. This is also the case, for example, with physiotherapist and researcher Danilo de Oliveira, who suffered an ACL and MCL tear five weeks ago. He was assessed and encouraged to undergo CPB by his colleagues at the Australian university of La Trobe. That's why I say "myself," and it doesn't mean it's for all patients in Spain. However, I strongly believe that those who have access to information and wish to do so should be able to choose CPB.

Is it yours? You must be aware of the level of commitment it will demand and that you will need a doctor, unsure if any in Spain will currently take this initiative, and a physiotherapist. Based on what has been discussed earlier, from the Knee Spain physiotherapists' network, we are already taking a step forward so that both doctors and patients can rely on us to carry it out. This way, the application of CPB can become a reality for those who choose it in Spain as well, and we may even contribute to its research.


CPB opens a window that may either yield no significant results or potentially lead us, in 20 years, to approach ACL injuries in a fundamentally different manner within a distinct paradigm. In the interim, if you have reached this juncture:

For Patients with ACL Injuries: CPB currently represents a potentially viable option for treating this injury, warranting further investigation and already being implemented in patients in countries like Australia. Due to the necessity for more conclusive results, it is not an approach that healthcare professionals can presently endorse. Nevertheless, this does not imply it is a contraindicated choice for patients who wish to pursue it, particularly if the structural nature of their injury aligns with specific characteristics. The sole drawback of its application lies in the delay in initiating a conservative or surgical approach. In this article, our aim is to have furnished you with comprehensive information on this subject, addressing any immediate misinterpretations that might have caused confusion. We encourage you to consistently adhere to the well-founded opinions of healthcare professionals.

For Doctors and Physiotherapists: We trust that this detailed information will assist you in forming an opinion on the potential for ACL healing and the current options available, as perceived by us, for patients who seek it. Perhaps, in the future, these options may be promoted by us as professionals if reliable results are demonstrated. If selected as an option, it is crucial to be cognizant that a protocol like CPB will necessitate specialized Traumatology and Physiotherapy, with one being inseparable from the other in its application.

Mervyn Cross passed away in August 2023. However, the possibility he introduced persists through the ongoing research that Filbay is conducting. We eagerly anticipate the information that the future will unveil, pledging our commitment to providing the best service possible to ACL patients in the present.

Acknowledgments: to Cristina González and Stephany Filbay for the review of this article.

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The Syndey Morning Herald: “Bend the knee: the game-changing procedure for athletes with ACL injury”

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British Journal of Sports Medicine Published Online First: 14 June 2023

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