If you are an athlete, then you know the importance of keeping your ACL healthy. The most common type of knee injury is to the ACL, or anterior cruciate ligament. The ACL is one of the most important ligaments in the body for performance, and it can be easily injured.

Recently, there has been a lot of research into stem cell therapy as a possible treatment for ACL injuries. In this blog post, we will discuss the latest research on this topic and whether or not stem cell therapy is a viable option for treating ACL injuries.

Why Doesn’t the ACL Heal Naturally?

The reason surgery is necessary in the first place is because the ACL is not able to heal itself. Unlike tendon and bone-related injuries, the lack of blood flow to the damaged tissue prevents adequate healing. However, with stem cell therapy, the hope is that the stem cells will be able to repair the ACL and allow it to heal properly.

Stem Cells

When discussing this therapy, it is imperative to first know what stem cells are. Stem cells are the raw materials from which all other specialized cells in the body are created. Stem cells divide under the proper conditions inside the body or in a lab to generate new daughter cells.

Daughter Cells

Daughter cells formed by stem cells might develop into either new stem cells or specialized cell types, such as blood components, brain elements, heart muscle tissues, or bone tissues (differentiation). No other cell in the body has this natural capacity to form new cell types.

Mesenchymal Stem Cells

Mesenchymal stem cells are multipotent stem cells that can differentiate into a variety of cell types, including cells derived from bone, cartilage, muscle, and fat. These unique cells can also be isolated from other tissues, including cord blood, peripheral blood, the fallopian tube, and the fetal liver and lung.

Stem Cell Therapy

Stem cell therapy is also referred to as regenerative medicine. This is because the goal of this therapy is to assist or amplify the body’s natural healing mechanism and repair damaged tissues and organs. This can be done by using stem cells that are injected into the damaged area.

The hope is that the stem cells will then divide and differentiate into the cell types that are needed to repair the damage.

Types of Stem Cell Therapy

Cells used or targeted by cell therapy can be classified into three categories: pluripotent stem cells (PSCs), adult stem cells (ASCs), and cancer stem cells (CSCs).

Pluripotent Stem Cells (PSCs)

There are four types of PSCs: embryonic stem cells, epiblast stem cells (EpiSCs), embryonic germ cells (EGCs), and induced pluripotent stem cells (iPSCs). ESCs are cells derived in the inner blastocyst cell mass of preimplantation embryos. EpiSCs and EGCs are found in postimplantation embryos. iPSCs are derived from direct reprogramming of postnatal/adult somatic cells.

Although embryonic stem cells and iPSCs are biologically and molecularly identical, the usage of embryonic stem cells is limited owing to ethical issues surrounding fetal lives.

Adult Stem Cells (ASCs)

Adult stem cells are rare, undifferentiated cells distributed among differentiated or specialized cells in the organs of a developed organism. With more limited self-renewal and differentiation potentials than PSCs, adult stem cells replenish lost cells or contribute to the healing or growth of cells by giving rise to precursor or progenitor cells and ultimately differentiated cells.

Cancer Stem Cells (CSCs)

CSCs are tumor-initiating cells that are found in both solid tumors and blood tumors. They come from normal stem cells or progenitor cells. This happens because of things like mutations, gene transfer, epigenetic alterations, and microenvironmental factors.

CSCs can renew themselves, differentiate, metastasize, and suppress the immune system. This makes them very important for cancer growth, metastasis, relapse, and resistance to chemotherapy and radiation therapy.

ACL Stem Cell Treatment

The type of stem cell procedure most applicable to ACL injury is autologous mesenchymal stem cell (AMSC) therapy. This is a type of adult stem cell therapy where the patient’s stem cells are used for the treatment of the soft tissue. The hope is that, because these are the patient’s cells, there will be limited side effects and the cells will be more likely to integrate into the existing tissue.

Surgical Alternative

Many patients are intrigued by the idea of minimally invasive treatment options to address the pain or discomfort that comes inherently with ACL surgery. Surgeries on various conditions and painful joints can make the entire process of rehabilitation feel like imprisonment within their own body.

ACL stem cell therapy presents a unique opportunity to those athletes and regular people, alike who seek an alternative to the traditional surgical process. A good candidate for this type of therapy is someone whose ACL has been torn or damaged, but the surrounding ligaments and tendons are still healthy.


Why an Alternative to Surgery?

There are various reasons a patient would prefer to avoid surgery. Below are a few of the most prominent reasons:


The length of time it takes to recover from such a surgery is a few weeks. It can be very difficult to take that much time away from work, family, or other important aspects or obligations of your life.

Pain Management

The second reason is the pain that is associated with ACL surgery and the rehabilitation process. Stem cell therapy would minimize the chronic pain that most patients endure while resting in the injured area, providing much-needed pain relief for the patients.


With any surgery, there is an inherent risk that the tissue or previously damaged area could become infected. This is slightly increased with ACL surgery because of the location of the surgery. Present literature displays that the current estimation is roughly 1.2% of ACL surgeries end in an infection of the affected area.

Blood Clots

Many recent studies have investigated the rate at which this particular procedure yields blood clots. One such study found that 8.4% of patients who didn’t receive adequate post-surgical medication had a deep vein thrombosis. Proper post-surgery pharmacological treatment is warranted to ensure the patient is not under elevated risk.

Continued Negative Symptoms

Whenever surgery is done on a particular joint, joint pain, various soft tissue conditions, and future degenerative conditions could arise. The procedure could also leave the patient with stiffness or loss of range of motion. If those symptoms aren’t addressed the patient could have chronic joint pain.

Graft Rejection

The final reason has to do with the ACL graft itself. When a new ACL is put in, there is always a chance that the body will reject the new tissue. This could lead to more surgeries and other procedures to fix the problem.

These additional treatments will compound the likelihood the patient has chronic joint pain and is unable to attain significant pain relief.

Stem Cell Procedure Process

ACL stem cell therapy begins with the collection of fat cells from around the patient’s hip area. These cells are then purified in a laboratory setting and concentrated. Once this is done, they are injected into the knee joint under ultrasound guidance.

The entire process from start to finish takes about two hours.


Most patients can walk within a few hours of the procedure and can return to their regular activities, including sports, within a few weeks. It is recommended that patients avoid high-impact activities for at least six weeks after stem cell therapy to allow the tissue to properly heal.

History of Stem Cell Procedures


In the year 1902, a Russian histologist named Alexander M. Maximow referred to stem cells (polyblasts) as “wandering cells at rest,” according to their history. From 1896 until 1902, Maximow produced papers describing his curiosity about blood and connective tissues. He supported the unitarian hematopoiesis theory and proved that all blood cells originate from a precursor cell.

In the Last Half Century

Since then, researchers from all over the world have experimented with stem cells (on mice, plants, and humans) in search of a cure for a variety of ailments, illnesses, and injuries. In 1969, Edward Donnall Thomas began the history of stem cell therapy and therefore regenerative medicine, by performing the first bone marrow transplant with stem cells taken from another person to evaluate the effect it would have on the healing process.

Stem Cell Treatment Today

Now, stem cell therapy is being used to treat a variety of injuries and conditions. It is also being studied as a possible treatment for Alzheimer’s disease, Parkinson’s disease, spinal cord injuries, heart disease, diabetes, and arthritis. In some cases, stem cell therapy is being used in conjunction with other treatments, such as surgery or medication.

While stem cell therapies are state-of-the-art and have the potential to minimize patients suffering, they are still new. Due to this newness, there is always the potential for unforeseen long-term risks, pain, and complications to occur.

Before deciding to undergo stem cell therapy or regenerative medicine, you must consult with your doctor to discuss all of the potential risks and benefits. Once you have decided that stem cell therapy is right for you, the next step is finding a reputable and qualified doctor who can perform the procedure.

Efficacy and Research

Many promising studies are pointing to the future of care with stem cell treatments, involving mesenchymal stem cells or bone marrow stem cells. Stem cell treatments, while less common, are still being completed in various places across the United States. Different states have different regulations, so it is important to check with your state’s medical board to see if the procedure is legal in your state.

Many of the studies and experts analyzing the effects of stell cell treatment have positive outcomes but with a caveat to the limitations of the study.

Ongoing Research

Like platelet-rich plasma, the effectiveness of stem cell therapy is still being researched, and there is no definitive answer at this time to help minimize the length of time most patients will require treatment and lower the time needed throughout the healing process.

Limitations of Present Literature

A large majority of studies that have been completed are small, meaning they don’t necessarily reflect how the therapy would work on a larger population. Additionally, most of these studies were sponsored by the companies that make the stem cell products being used in the study. Larger and more definitive studies are needed to better understand how effective stem cell therapy is and how it can be best utilized in the medical field.

Most Common Musculoskeletal Injuries Injuries Treated

At this time, stem cell therapy is most commonly used to treat:

ACL Injuries

– Rotator Cuff Injuries

– Knee Injuries and Arthritis

– Shoulder Injuries and Arthritis

– Hip Injuries and Arthritis


The reasons one would choose to utilize stem cell injections rather than other options are because of the lower risk for infection, minimal pain during and after the procedure, as well as a shorter recovery time. A good candidate for stem cell treatment in patients with various degenerative conditions, soft tissue injuries, or ligament tears.

Overall, stem cell therapy for ACL injuries is a promising new treatment for a variety of injuries and conditions. While it is still new and more research is needed to definitively prove its effectiveness, many people have found relief from pain and suffering after undergoing stem cell therapy.

Schedule an Appointment

If you are considering this treatment, be sure to consult with your doctor and schedule an appointment first to discuss all of the potential risks and benefits. Once you have decided that stem cell therapy is right for you, the next step is finding a reputable and qualified doctor who can perform the procedure. With so many studies pointing to the future success of stem cell treatments, it is an exciting time for regenerative medicine.

About the Author

Hi there! I’m Dr. Keagen Hadley, OTD, OTR/L. Straight out of the University of Mary, I’m all about blending my know-how in knee health, well-being, and medical technology. As a licensed occupational therapy doc, I’m here to translate complex concepts into clear, actionable insights – whether it’s knee care or groundbreaking healthcare tech.

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