Complete or a partial ACL tear, is ACL surgery necessary?

Ross A. Hauser, MD, Danielle R. Steilen-Matias, MMS, PA-C.

ACL reconstruction surgery alternatives and regenerative treatment options

Is ACL reconstruction surgical repair the right option for every patient? In this article, we review the latest medical research that can help the patient/athlete understand their ACL pre and post-surgery challenges. If you are reading this article you may be debating whether to have surgery or not or that you are on the waiting list to get surgery. One option for treatment we will explore is regenerative medicine, non-surgical treatment options, and the realistic assessment of whether or not this can help you.

People who get ACL reconstruction surgery can have excellent results. These are not the people we see in our office. We see the people for whom the promise of ACL reconstructive surgery did not offer the same excellent results. We see the people who have had an ACL reconstruction, ACL reconstruction with meniscus repair, and second or revision ACL surgery for a rupture of the “fixed” ACL. We see the people for whom ACL surgery was not the answer and they need help. Now they are exploring options to either get them back to sports or to try to avoid what they were told was the inevitable advancement of osteoarthritis.

We also see the people who have to decide whether should they have the surgery or not. These are people who debate whether or not the surgery will be worth it for them and the long rehabilitation it implies. These may be people who have an urgency to return to sport before academic eligibility expires or the people who do a physically demanding line of work and have to way surgery versus other options to keep them on the job.

  • If you have a question about ACL surgery options – email us now.

Summary points of this article:

Part 1: Is the MRI accurate?

  • Does the MRI correctly see the ligament damage? Does it see “too much?”
  • Do you really have a complete ACL tear? Is your MRI accurate? It is two out of three times.

Part 2: Early ACL reconstruction or a primary physical therapy plan with optional reconstruction surgery later if needed?

  • Some people do not need ACL reconstruction surgery to return to play. “Whether surgical or conservative treatment is more effective in allowing patients to return to physical activity after anterior cruciate ligament (ACL) injury is controversial.”
  • When do conservatively treated partial ACL tears progress to full-blown ruptures?
  • Partial ACL tear progressed to a complete tear in 47.3% of evaluated patients.

Part 3: Returning to sports without surgery. A reality or fantasy?

  • “Despite common misconceptions to the contrary, research suggests that it is possible for an individual who suffers an ACL rupture to return to sport following management with rehabilitation alone.”
  • Early Return to Play Not Recommended for Student-Athletes – WITHOUT RECONSTRUCTION – More damage to meniscus and cartilage

“Is ACL reconstruction really necessary?” “Can I get by without an ACL?” For many people, the hardest part of their ACL injury is the decision of what to do about it and waiting for a surgery date.

For the young athlete who has an aspiration for a college athletic career, seemingly there is no choice but surgery. For the high school sophomore who wants to play their senior year and finish their youth sports career on the field, there seems to be only one choice, surgery. But what about the older recreational athlete, what about the person who works at a physically demanding job? What about the older patient? Is ACL reconstruction really necessary?

Someone who is debating surgery or no surgery will come into our clinics and tell a story that sounds like this:

My surgeon wants me to try physical therapy first as she suggested people can live without an ACL.

My MRI confirmed that I have a torn ACL and a meniscus tear. My surgeon wants me to try physical therapy first as she suggested people can live without an ACL and do so happily. If my knee felt unstable, not right, or caused me any functional problems, and/or I had to alter my lifestyle, then the ACL reconstruction surgery should be performed. Simultaneously the meniscus should be dealt with.

I was fitted for a “better brace.”

The PT seemed to go very well, I was fitted with a large brace, had a three-a-week schedule of PT, and felt really good. While I felt my leg getting stronger, I realized that my knee remained unstable. I was fitted for a “better brace.” Now here I am looking for a non-surgical answer to my knee instability if one exists. (A person like this is seeking stability treatment for the whole knee, this means an examination of all the existing ligaments and a plan to strengthen those – see below).


Part 1: Is the MRI accurate?

Was the MRI of a complete ACL rupture even accurate?

Let’s look back at two decades of research into the accuracy of MRI for detecting a true MRI tear. The question of is an MRI actually showing a complete or partial rupture in some cases remains controversial and debated. Let’s jump into this debate starting in 2007 and take it to 2024.

In 2007, doctors writing in the British Medical Bulletin (1) wrote: “MRI is highly accurate in diagnosing meniscal and anterior cruciate ligament (ACL) tears. It is the most appropriate screening tool before therapeutic arthroscopy (exploratory and fix-it surgery). It is preferable to diagnostic arthroscopy in most patients because it avoids the surgical risks of arthroscopy. The results of MRI differ for medial and lateral meniscus and ACL, with only 85% accuracy.” So the suggestion is MRI is very good, but not quite perfect. Now of course that research is from 2007. There has been fantastic progress since then. In fact, there has been so much progress that the question now has to be asked: Does the MRI correctly see the ligament damage? Does it see “too much?”

Does the MRI correctly see the ligament damage? Does it see “too much and mistake the severity of the tear?”

What does it mean when we suggest the MRI is seeing too much? It means that the MRI took a picture and the radiologist’s interpretation suggests a full-blown tear when a full-blown tear may not be there. In January 2022, doctors writing in the journal BioMed Central Musculoskeletal Disorders (2) assessed the accuracy of MRI in diagnosing and classifying acute traumatic multiple ligament knee injuries. Here is what they wrote:

“Magnetic resonance imaging (MRI) is widely used for the evaluation of knee injuries, however, the accuracy of MRI in classifying multiple ligament knee injuries remains unknown.” (In other words the study’s authors are saying, we do not know how accurate this is).

Therefore, their study’s goals aimed to investigate the accuracy of MRI in diagnosing and classifying acute traumatic multiple ligament knee injuries. The study authors noted that they went into this study believing that the MRI had high accuracy in detecting and classifying multiple ligament knee injuries. Let’s see if those beliefs are founded.

The doctors looked at 97 patients who were diagnosed with acute traumatic multiple ligament knee injuries and managed by multi-ligament reconstruction. The MR images were read by two experienced radiologists and results were compared with intraoperative findings, which were considered as the reference for the identification of injured structures.

Results: For detecting the specific injured structures in multiple ligament knee injuries, MRI had high sensitivity (90.7% for ACL, 90.4% for PCL, and moderate specificity (63.6% for ACL, 50% for PCL).

What does this mean?

Sensitivity for MR imaging to identify something that MAY be a tear was at 90%. Meaning that the MRI interpretation was correct in seeing a tear 90% of the time. The significance of the tear, full or partial, then because less odds-worthy. Moderate specificity for the ACL tear means that when these 90% of people were separated into probable and non-probable (specific to the type of tear, hence the word specificity) 63.6% of the time the tear was correctly identified. About two out of three times.

A February 2023 paper in the American Journal of Sports Medicine (3) did suggest however that while MRIs have “shown limited diagnostic accuracy for multiple ligament knee injuries” . . .   ACL tears ACL), showed the best diagnostic accuracy (94.4%) versus diagnosing other multiple ligament knee injuries in trauma injury. While the ACL tear was seen with high accuracy, the researchers noted that “diagnostic accuracy of MRI for multiple ligament knee injuries largely varied among knee structures, with many of them at risk of a misdiagnosis, especially posterolateral corner, meniscal, and chondral lesions (injuries).”

2024, MRI’s, artificial intelligence, and lesser experienced technicians.

The point of this section was to demonstrate that the MRI, in some cases, may not reveal what is actually going on in the knee and care should be taken in perusing treatment options. Of note is an August 2023 paper (4) which introduced artificial intelligence (AI) into the equation. Here researchers recruited clinicians of varying expertise levels in sports medicine and radiology to test their capacities in diagnosing ACL injuries in terms of accuracy and diagnosing time. The researchers found that AI assistance significantly improved the accuracy of all clinicians, exceeding 96%. “The most significant improvements in accuracy and time efficiency were observed in the trainee groups, suggesting that AI support is particularly beneficial for clinicians with moderately limited diagnostic expertise.” Even still, about 1 in 25 MRI readings were not accurate.

Part 2: Early reconstruction or primary physical therapy with optional later reconstruction. Getting players back to the sport as quickly as possible.

In August 2023, German sports trauma specialists (5) wrote: “The aim of treatment of a ruptured anterior cruciate ligament (ACL) is the return of the patient to an acceptable level of activity without giving way phenomena as well as adequate treatment of prognostically relevant concomitant lesions.” In other words, provide stability and make sure other ligaments or meniscus injuries do not impede the healing of the knee. Continuing, “The treatment of acute ACL ruptures can be either early reconstruction or primary physiotherapy with optional later reconstruction. Which path is taken depends on possible concomitant injuries that require early surgical intervention (e.g., repairable meniscal injury or distal rupture of the medial collateral ligament) and on patient-specific factors (age, level of activity). Isolated ruptures of the ACL can also be primarily treated without surgery.” So here we have an important distinct in when ACL injuries may or may not need surgery. An ACL tear in isolation falls into the category of possibly not needing surgery to return to activities.

ACL Therapy

Some people do not need ACL reconstruction surgery to return to play. “Whether surgical or conservative treatment is more effective in allowing patients to return to physical activity after anterior cruciate ligament (ACL) injury is controversial.”

Let’s explore the surgery and non-surgery angle better: A paper published in December 2017 (6) weighed in on the ACL Surgery or Not Debate.

The doctors of this study noted: “Whether surgical or conservative treatment is more effective in allowing patients to return to physical activity after anterior cruciate ligament (ACL) injury is controversial. We sought to compare mid-term outcome measures between isolated ACL tear patients who underwent reconstruction followed by closed kinetic chain exercises and those who underwent neuromuscular training only.”

Okay so in this study, what was the outcome? No statistical difference was observed.

“No statistical difference was observed between the groups for any of the parameters evaluated, including assessment of subjective knee function, one-leg hop test, assessment of joint position sense, muscle strength, and the health profile.”

The conclusion?

“(Study) data suggest that early surgical reconstruction may not be a prerequisite to returning to recreational physical activities after injury in patients with ACL tears.”

For some people, you do not need ACL reconstruction surgery to return to play.

We do realize that this is a hot-button suggestion and that many people will point to professional athletes as proof of the need for an ACL reconstruction surgery. Please keep reading, there is so much more to discuss.

A January 2022 study in the journal Arthroscopy, Sports Medicine, and Rehabilitation (7) suggested that following ACL reconstruction, about 80% of patients return to some type of sport, but only 65% return to preinjury levels of participation, and only 55% return to competitive sport. People with ACL injuries do have options to choose from besides surgery. These options typically include therapies to compensate for the ACL damage by strengthening the surrounding areas of the knee.

When do conservatively treated partial ACL tears progress to full-blown ruptures?

A 2019 study in the Orthopaedic Journal of Sports Medicine (8) assessed the incidence and risk factors for the progression of partial ACL tears to complete ruptures after nonoperative treatment in active patients younger than 30 years old. Here are the observations and learning points of this study:

  • “The most important finding of the current study was that in young active patients with partial ACL tears treated nonoperatively, 39% progressed to a complete tear at a mean of 43 months after the first injury. (Patients under 20 years old) and participation in pivoting contact sports were significant predictive factors for failure of conservative treatment, that is, progression to a complete ACL tear. Meniscal lesions were found in 50% of cases that progressed to a complete ACL tear.”

The initial finding is that about four out 10 ten younger patients with a partial ACL tear would eventually see that tear progress to a full rupture on average about 3.5 years after the partial tear diagnosis.

Patients under 20 who participated in pivoting contact sports (soccer, basketball) were at higher risk and when they ruptured their ACL, meniscus damage was discovered that occurred previous to the rupture injury or was part of the rupture impact.

Returning to the research:

  • “The diagnosis of a partial ACL tear remains controversial because there is no single “gold-standard” method, but rather, the diagnosis tends to rely on a combination of findings.”
  • “(Studies) have suggested that partial tears of the ACL are functionally equivalent to complete tears and that nonoperative management generates poor results. Many authors have reported ACL deficiency rates of 14% to 56% after the nonoperative management of partial tears.”
  • “Nonoperative treatment has its particular indications and reasonable results, but the typical patient profile has changed. Patient expectations of long-term sports participation have grown exponentially in tandem with increased longevity. In addition, patients are increasingly aware of how much time they will be out of work or away from their sport and how these periods may differ between nonoperative and operative approaches.”

Partial ACL tear progressed to a complete tear in 47.3% of evaluated patients

In April 2023, surgeons and researchers wrote in the Archives of Orthopedic and Trauma Surgery (9): “Partial ACL tear progressed to a complete tear in 47.3% of evaluated patients.”

In this study group, the risk factors for progression to full tear were:

  • Being less than 35 years old.
  • “Rigorous physical activities.
  • “High ACL-Return to Sport after Injury score” during early rehabilitation days. This test or evaluation assesses the person’s mental readiness to return to sport following ACL injury.
  • Early return to activity, and pivoting contact sports.

Part 3: Returning to sports without surgery. A reality or fantasy?

Football Hall of Famer Joe Namath is believed to have played his entire NFL career without an ACL. However the damage to his knees were legendary and resulted in knee replacements. The brace on his right knee is clearly visible.
Football Hall of Famer Joe Namath is believed to have played his entire NFL career without an ACL. However, the damage to his knees was legendary and resulted in knee replacements long after his career ended. The brace on his right knee is clearly visible in the above photo.
Football Hall of Famer John Elway played his entire career without an ACL in his left knee. (The one that is very bent above.) Like Namath, Elway suffered his injury at a time when ACL injuries were career-ending.
Football Hall of Famer John Elway played his entire career without an ACL in his left knee. (The one that is very bent above.) Like Namath, Elway suffered his injury at a time when ACL injuries were considered career-ending.

“Despite common misconceptions to the contrary, research suggests that it is possible for an individual who suffers an ACL rupture to return to sport following management with rehabilitation alone”

Here is a 2019 study from the University of Oxford, Oxford, and the Norwegian School of Sport Sciences. (10) The question being asked is “Do the outcomes of ACL rupture differ depending on management strategy?” Here are the learning points of this research:

  • “There are a number of literature reviews comparing outcomes between individuals that are ACL-deficient or have had an ACL reconstruction surgery. It is important to note that most studies included in these reviews do not reflect best practices for the nonoperative management of ACL rupture. For example, many of the nonoperatively managed patients in these studies received a diagnostic knee arthroscopy, some were advised to reduce activity levels, and rehabilitation was often not monitored, of low intensity or short duration, or included post-injury immobilization with a brace or cast.”
  • Here is the learning point: “Despite this, these literature reviews report similar outcomes in ACL-deficient and ACL-reconstructed groups, including similar patient-reported outcomes, knee function, activity levels, quality of life, and either no difference in radiographic osteoarthritis prevalence or a slightly increased prevalence following ACL reconstruction surgery.” We are going to see this again, ACL reconstruction surgery increases the risk of osteoarthritis.

Here the researchers go further in the surgery or no-surgery debate.

“Despite common misconceptions to the contrary, research suggests that it is possible for an individual who suffers an ACL rupture to return to sport following management with rehabilitation alone. Several studies have found no difference in physical activity levels or return to sport rates between patients managed with ACL reconstruction surgery and those managed with rehabilitation.”

Early Return to Play Not Recommended for Student-Athletes – WITHOUT RECONSTRUCTION – More damage to meniscus and cartilage

A November 2021 study in the Progress in Rehabilitation Medicine (11) investigated whether student-athletes with anterior cruciate ligament (ACL) injuries who returned to sports without reconstruction could continue their sporting activities until the end of the season and whether there was an increase in secondary damage associated with knee instability.

How was the study done?

  • 288 skeletally mature patients under the age of 25 years old with new-onset isolated primary ACL injuries were included.
  • Of these, 20 student-athletes continued playing sports without ACL reconstruction to try to finish the season and were classified as the early return to sports group; the remaining 268 patients, who immediately quit sports and underwent surgery, were classified as the non-early return to sports group.
  • Knee symptoms and sporting performance for the rest of the season were assessed for the early return to the sports group. The presence of secondary damage, e.g., meniscus injuries and chondral lesions, associated with instability were compared between the two groups.


  • Fourteen early return to sports-group athletes (70%) indicated that their knees had given way during sporting activities, and seven athletes (35%) were unable to complete the season.
  • Despite the early return to sports period being relatively short, medial meniscus tears significantly increased in the early return to sports group, and three patients experienced locking of the medial meniscus and required immediate surgery.


  • Although an early return to sports without reconstruction to complete the season may be a reasonable strategy for ACL injury, patients’ self-estimated performance level was low, and meniscal and cartilage injury rates significantly increased.

A ruptured ACL can spontaneously heal. But not for everyone.

A January 2023 study in the British Journal of Sports Medicine (12) found that on an MRI before and after, ACL healing after ACL rupture occurred in one in three adults randomized to initial rehabilitation (did not have surgery) and one in two who did not cross-over to delayed ACL reconstruction and was associated with favorable outcomes. The researchers noted: “The potential for spontaneous healing of the ACL to facilitate better clinical outcomes may be greater than previously considered.”

An October 2023 paper in the International Journal of Sports Physical Therapy (13) suggests “satisfactory functional results after spontaneous healing of a ruptured anterior cruciate ligament (ACL)” is possible, but “there is still a lot to understand in how an injured ACL may heal, and therefore ACL injury management should be individualized to each patient and carefully discussed.”

So what about this spontaneous healing?

The authors do suggest that many factors could allow an ACL to spontaneously “rebuild itself.” However, they note, “these events are very dependent on part of the ACL and its sheath remaining connected between the femur and the tibia. . . There is evidence that conservative treatment can be successful in the general population, with some people healing their ACL. This is not the case for elite athletes. The emerging evidence regarding the ability for the ACL to heal is intriguing and may change clinical practice in the future, but we urge clinicians to take these results with extreme caution as this may only be suitable for a very small percentage of the population.”

In July 2023, German surgeons and health care providers noted in the Archives of Orthopaedic and Trauma Surgery (14) “Spontaneous healing of a ruptured ACL happened in 14% of the patients. Especially in low-demand patients with femoral single bundle lesions (ACL tears typically treated with a single bundle (one tendon transplant) without increased posterior tibial slope (Knee is more anatomically correct). . . ”Delayed ACL surgery should be considered to await the possibility for potential spontaneous ACL healing . . .” However the surgeons noted: “However, patients with spontaneously healed ACL showed a significantly decreased stability compared to the non-injured side.”

The complexity of an ACL tear – Is it full? Partial? Can it regenerate on its own in the proper circumstances?

In 2009, Prolotherapy doctors (see below for an explanation of prolotherapy treatments) led by Walter Grote MD published a case history of an 18-year-old female patient who returned to sports after a high-grade partial (possibly complete) ACL rupture.

This case report, published in the medical journal International Musculoskeletal Medicine, (15) documented the successful non-surgical repair of an MRI-confirmed high-grade or total ACL tear in an 18-year-old female with knee laxity and instability using Prolotherapy and at-home exercise. After treatment, the patient regained full knee function, resumed normal activity, and returned to recreational sport. Post-treatment MRI revealed a healing chronic ACL tear. These findings are notable given that surgical ACL reconstruction is the conventional treatment for ACL tears with such clinical presentation.

As exciting as this sounds, Dr. Grote and colleagues noted that there were too many factors in this ACL healing to confirm it was caused by Prolotherapy treatment alone. Listen carefully to what this case history presented:

The conclusion: The limitations above prevent a categorical conclusion that Prolotherapy alone contributed to or restored pain-free function and improved the appearance of the MRI. However, the facts of this case and the context provided by prior clinical trials suggest that Prolotherapy at least augmented the healing of a high-grade or total ACL tear. These findings further suggest that Prolotherapy may be an alternative treatment to surgery for carefully selected patients and should be assessed as a treatment of ligamentous tears, especially in patients who are unwilling or unable to undergo surgical intervention.”

A father tells the story of his daughter, a High School age softball player who had attracted college attention.
She tore her ACL

While this is a typical case history, the results may not be typical for everyone.

  • The daughter was an avid, talented softball player. She suffered a skiing accident. At the time of the accident, she was entering her High School senior year and was already examining offers from numerous colleges that were recruiting her for softball.
  • The injury was an ACL injury. Two surgeons independently recommended ACL surgery as the only option. The rehab time would be about a year. She would lose her senior year of High School softball and the opportunity for college coaches to see her play.
  • My wife started to do a lot of research as my daughter was devastated. In her research, my wife found Dr. Hauser. We took a flight out of New York to Caring Medical in Chicago. After the examination, our daughter was deemed to be an appropriate candidate for Prolotherapy treatment because she DID NOT have a full detachment of the ACL.
  • After the one-day treatment, she was sent home to New York with the instructions to RESUME activity. She was a catcher. She started catching immediately, with no problems.
  • 4 weeks later the family returned to Chicago so the daughter could have another treatment.
  • The story ends, with my daughter being able to play her senior year of High School at the catcher’s position. She entertained numerous college offers and accepted one to a Division 1 school. She played all 4 years and caught at least 70 games. During her college career, she had a few Prolotherapy treatments to keep her knees strong. Seven years later she continues to play tennis and various sports.

Biomaterials Prolotherapy, PRP, and stem cells in partial ACL tears

When discussing non-surgical applications of regenerative medicine such as bone marrow-derived stem cell therapy, Platelet-rich Plasma therapy, or Prolotherapy, discussions must be tempered with the realistic indications and outcomes that may be expected from these treatments.

  • These regenerative medicine injections cannot regrow an ACL from nothing. If there is a complete disintegration of the ligament, one cannot be regrown. The goal of these treatments is to help with a partial tear or overstretched ACLs. These treatments can restore strength and function to this type of ACL damage in many patients.
  • Further, these treatments are designed to strengthen the entire knee capsule. All the ligaments should be treated to help the partial or stretched ACL heal, or if ACL reconstruction or more ACL reconstruction surgeries are declined by the patient, strengthening the knee capsule may help prevent knee instability and more rapid degenerative arthritis from developing.

What is Prolotherapy and where is the research? Please visit our Prolotherapy research page for extensive and detailed information.

Prolotherapy is a “new” old treatment that has been utilized in clinical practices for over 80 years. Standardized and reviewed in clinical application by Dr. George Hackett in the 1950s, Prolotherapy has been shown to be an effective treatment in patients who suffer from joint instability due to ligament damage and overuse and related musculoskeletal and osteoarthritis. Prolotherapy’s popularity as a treatment for chronic pain has intensified over the past two decades among both physicians and patients as clinical and anecdotal observations have proved in many cases its reliance as a non-surgical option for joint and back pain.

  • Prolotherapy is a nonsurgical regenerative injection technique that introduces small amounts of an irritant solution to the site of painful and degenerated tendon insertions (entheses), joints, ligaments, and in adjacent joint spaces during several treatment sessions to promote the growth of normal cells and tissues.

Irritant solutions most often contain dextrose (d-glucose), a natural form of glucose normally found in the body.

In January 2017, doctors writing in the Orthopedic Journal of Sports Medicine wrote of the controversies surrounding the repair of partial ACL tears. One of the controversies was reconstructive surgery. In this study, the researchers found that biologically augmented ACL-repair techniques (PRP and stem cells) improve healing and outcomes of both the native ACL (non-surgery) and the reconstructed graft tissue (surgery). (16)

In 2003, K. Dean Reeves, MD published in the journal Alternative Therapies in Health and Medicine (17) these findings:

  • 16 knees with machine-measured ACL laxity were injected bimonthly with 10-25% dextrose solution (Prolotherapy) for 1 year and then an average of 4 times yearly thereafter until 3-year follow-up.
  • Summary: Using simple dextrose injection into 16 knees with a loose ACL ligament,
    • 10/16 knees were no longer loose by machine measurement at the time of follow-up, and symptoms were improved.
    • A symptom of osteoarthritis improved even in those who still tested loose.
    • At the 3-year follow-up pain with walking had improved by 43%, subjective swelling improved by 63%, flexion range of motion improved by 10.5 degrees, and machine measure of ACL ligament looseness improved by 71%.

PRP injections or ACL Surgery in older patients?

An August 2022 study in the European Journal of Translational Myology (18) a publication dedicated to the study of joints and muscles, writes: “In old patients with ACL rupture, surgery is not recommended due to the person’s low level of activity and knee osteoarthritis. Platelet-rich plasma (PRP) is a good treatment option in inflammatory cases in orthopedics. Hence, the aim of this study was to assess and comparison of the effect of PRP and arthroscopic surgery on anterior cruciate ligament rupture.

  • 100 patients were randomly divided into two groups.
    • The first group of patients underwent ACL tendon repair surgery by arthroscopy and tendon graft.
    • The second group was treated by PRP injection.
    • Both groups of patients were visited from 3 months to 14 months after surgery or PRP treatments.
  • Patients in both groups had significantly decreased pain severity after 14 months, but the patients in the surgical treatment group had significantly lower pain and a higher Range of motion compared to the PRP group.

How we examine for knee instability under ultrasound. Here we discuss the meniscus which is commonly injured in ACL tears.

The realities of non-surgical ACL regeneration
Stem Cell Therapy and Prolotherapy  – Non-surgical ACL reconstruction?

Stem Cell Therapy involves direct bone marrow aspiration (or also concentrated) to get the stem cells to the site of the injury. We use bone marrow stem cells in conjunction with other Prolotherapy solutions to treat large articular defects in the meniscus areas. Typically, patients are seen every two months. Most patients need 3-6 visits. The good news is during the time of healing, the patient can exercise and start getting back into great shape.

Doctors at the Department of Trauma Surgery and Sports Injuries, University Hospital of Salzburg wrote in the Archives of Orthopaedic and Trauma Surgery:

“The ACL has the potential to heal upon intensive non-surgical rehabilitation procedures. Several biological factors influence this healing process as local intraligamentous cytokines (messengers that call for more inflammation (healing)) and mainly cell repair mechanisms controlled by stem cells or progenitor (creator) cells. Understanding the mechanisms of this regeneration process and the cells involved may pave the way for novel, less invasive, and biology-based strategies for ACL repair.”(19)

In 2015, doctors in China excitedly published research in the Chinese Journal of Reparative and Reconstructive Surgery which said: “Enormous progress has been made in tissue-engineered ligament for repair and regeneration of ACL. With the development of biochemistry and scaffold materials, the tissue-engineered ligament will be used in clinics in the near future.”(20)

This research suggests that one day doctors will be able to grow a new ACL in the laboratory and implant it into a knee. That is fantastic news for the people of the future but what about today? Is there a way today to non-surgically repair a damaged ACL? Do you even need to replace the ACL?

Another team of Chinese researchers writing in the medical journal International Orthopaedics noted that the ACL has certain self-healing abilities after acute injury. These self-healing abilities have to do with stem cells (for a detailed discussion on how stem cells work please see my article on stem cell therapy). The Chinese team suggested that leaving behind part of the ruptured ACL remnant would release native stem cells into the new graft and augment healing. In addition, taking stem cells from the remnant ACL may be a potential source of seeding cells for ligament regeneration. (21)

This research found agreement in the work of Korean doctors who wrote in the medical journal Current Stem Cell Research and Therapy of recent developments in mesenchymal stem cell (MSC)-based approaches for enhancing healing after ACL injuries. They suggest that stem cells are a promising treatment option for enhancing the biological healing of ACL grafts and restoring the functional properties to the levels of the native ACL, and ultimately improving clinical outcomes. (22)

What this research suggests is stem cell augmentation for the ACL graft to prevent ACL complications.

The ACL and PCL (posterior cruciate ligament). The problems of identifying the source of ligament laxity and knee instability

The anterior cruciate ligament sits in front of the PCL and together the ACL and PCL  keep the tibia (shin bone) from sliding too far forward and the tibia in the position below the femur (thigh bone). The PCL is the knee’s basic stabilizer and is almost twice as strong as the ACL.

This illustration describes the interaction between the various knee ligaments and how together they provide stability or instability to the knee.
This illustration describes the interaction between the various knee ligaments and how together they provide stability or instability to the knee.

A 2018 study in the Journal of Surgery discusses the problems of identifying the true nature of knee instability causes and this research surrounds the PCL (23).

The researchers noted that “ACL tear in concomitant chronic ACL and posterior cruciate ligament (PCL) deficient knees may produce knee laxity, which is more difficult to assess on clinical examination, which in turn may affect the management algorithm of the patient.”

In our article Posterior Cruciate Ligament Injury and Treatments, we identify this problem and discuss the treatment of PCL damage. Briefly, we suggest: “Posterior cruciate ligament (PCL) injuries make up between 3 and 20 percent of all knee ligament injuries. However, PCL injuries are often left diagnosed. Why it is left undiagnosed and untreated is because the PCL is not well understood.”

Understanding and strengthening the PCL is an important factor in ACL-injured knees.

    • The inaccuracy of MRI is well documented, in this case, the study could not be relied on to give an accurate reading. Please see my article on MRI accuracy for determining the need for surgery. In this study, while MRI suggested a complete rupture, it may not have been a complete rupture.

All the ligaments of the knee work to stabilize an ACL injury and ACL-deficient knee

The ACL’s job is to prevent the tibia and the femur from moving excessively on each other. When it is injured or not there, it puts stress on the other ligaments to prevent this excessive motion.

If you are debating ACL reconstruction because of long rehabilitation, or unsureness that the surgery will be successful, already had one ACL reconstruction. Please consider a consultation. What we will discuss with you is:

  • Surgery or non-surgical approaches
  • The use of Prolotherapy, PRP, or stem cell treatments
  • A realistic expectation of surgery and non-surgical treatment

Summary and contact us. Can we help you?

We hope you found this article informative and that it helped answer many of the questions you may have surrounding your knee problems.  If you would like to get more information specific to your challenges please email us: Get help and information from our Caring Medical staff


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This article was updated October 30, 2023

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