Understanding ACL Tear: Why It Happens And What To Do Next
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An anterior cruciate ligament (ACL) tear is a common knee injury, particularly among athletes, with female athletes facing a higher risk due to a combination of anatomical and biomechanical factors. The annual reported incidence in the United States alone is approximately 1 in 3500 people. There are approximately 400,000 ACL reconstructions every year in the united states. This injury occurs when the ligament, which is key to stabilizing the knee joint, is overstretched or torn.
A torn ACL can make the knee feel unstable and affect movement. Knowing the causes, symptoms, and treatment options can help people manage the injury and protect their knee long-term.
Anatomy And Function Of Anterior Cruciate Ligament (ACL)
The ACL is one of two cruciate ligaments within the knee joint. These ligaments intersect, creating an “X” shape, with the ACL positioned at the front and the posterior cruciate ligament (PCL) at the back.
The ACL supports knee stability by helping to prevent the tibia (shinbone) from moving too far forward relative to the femur (thighbone). The PCL complements this function by limiting excessive backward movement of the tibia. Together, these ligaments help maintain proper knee alignment and support controlled movement.
What Does A Tear In The ACL Mean?
An ACL tear is a significant knee injury that can affect stability, mobility, and overall function. Because the ACL plays a key role in controlling knee movement, a tear may lead to pain, swelling, and a feeling of instability. Activities that involve running, jumping, or pivoting can become challenging. In some cases, the knee may give way during movement.
Types Of ACL Tears
ACL tears vary in severity and are classified based on the extent of the damage:
- Partial-thickness ACL tear: A partial tear damages the ligament but does not fully rupture it. Imaging shows some intact fibers, and knee stability may be compromised.
- Full-thickness non-retracted ACL tear: A complete tear severs the ligament, but the ends remain aligned and do not pull apart. Some knee stability may remain.
- Full-thickness retracted ACL tear: A full tear completely separates the ligament, causing the ends to retract. This often leads to significant knee instability and impaired function.
Common Triggers For Knee Ligament Problems
Several factors contribute to ACL tears, often involving movements that place excessive stress on the knee. Recognizing these common triggers can help reduce the chance of injury.
Common causes include:
Sudden Changes in Direction
A leading cause of ACL tears occurs when an athlete pivots suddenly while their feet are planted. This abrupt motion places excessive strain on the ligament, increasing the risk of injury. Sports like soccer, basketball, and football often involve rapid direction changes, making athletes more vulnerable to this type of stress on the knee.
Falls
ACL tears can occur when a fall involves a twisting motion or a direct impact to the knee. The sudden force may overstretch or rupture the ligament. This is especially common in sports like skiing, where falls are frequent, and in accidents that cause abrupt shifts in body weight and balance.
Hyperextended Knee
A hyperextended knee occurs when the joint is forced beyond its normal range of motion, causing the ACL to overstretch or tear. This often happens during running or jumping, especially if the knee is pushed backward upon landing. Hyperextension places significant stress on the ligament, increasing the risk of injury.
Direct Blows To The Outer Knee
A direct impact to the outer knee, common in contact sports like rugby or football, can put excessive stress on the ACL. This force may destabilize the joint, increasing the risk of a tear. Such injuries often occur during tackles or when the knee is struck by another player or object.
How To Recognize The Symptoms Of Ligament Damage
Recognizing ACL tear symptoms is essential for early intervention. Common signs include:
- Audible popping or grating sounds: A sudden “pop” or grating noise at the time of injury, often signaling ligament damage.
- Swelling or inflammation: Rapid swelling around the knee, typically developing within hours.
- Pain during movement: Discomfort that can worsen with weight-bearing or knee movement.
- Weakness or instability: A feeling of the knee giving way, making movement difficult.
- Restricted range of motion: Difficulty bending or straightening the knee due to pain or swelling.
- Side-Of-Knee Pain: Pain on the side of the knee may result from ligament injuries, iliotibial (IT) band syndrome, or meniscus issues. Accompanying symptoms can include tenderness, swelling, and discomfort, often worsening with movement or prolonged activity. Read More About Side-Of-Knee Pain.
- Can’t Straighten Knee: Difficulty fully extending the knee may be due to joint stiffness, a meniscus tear, ligament injury, or arthritis. It can cause discomfort, swelling, or a locking sensation, limiting mobility and daily activities. Read More About Can’t Straighten Knee.
- Knee Hyperextension: Knee hyperextension occurs when the knee bends backward beyond its normal range, often due to ligament laxity or injury. It may cause pain, swelling, and instability, increasing the risk of further joint damage. Read More About Knee Hyperextension.
Avoid Complications Through Prompt Medical Attention
Getting timely medical care for an ACL tear is essential for proper diagnosis and management. A thorough assessment by a physician can help determine the extent of the injury and reduce the risk of further damage.
If left untreated, an ACL tear may lead to complications such as:
- Chronic knee instability: Ongoing instability increases the risk of further knee injuries.
- Osteoarthritis: Repeated joint instability can contribute to early-onset osteoarthritis, leading to pain and stiffness.
- Meniscus damage: A torn ACL may also lead to meniscus injuries, further affecting knee function.
- Reduced mobility: Untreated ACL injuries can limit the range of motion, impacting daily activities and athletic performance.
Diagnosing Torn ACL
Accurately diagnosing an ACL tear requires a combination of physical examination and advanced imaging. Physicians typically begin with a medical history review and physical tests to assess knee stability.
Standard diagnostic methods include:
- Physical exam: Tests like the Lachman test or anterior drawer test help evaluate knee stability.
- X-rays: X-rays are used to rule out fractures, though they do not show ligament damage.
- MRI (magnetic resonance imaging): MRI provides detailed images of soft tissues, making it the most accurate tool for diagnosing ACL tears.
- Ultrasound: Musculoskeletal ultrasound may be used to assess surrounding soft tissues in real time. While it cannot visualize the ACL as clearly as MRI, it can help identify joint effusion, related ligament injuries, or tendon damage and may be useful as a supplemental or initial imaging tool in certain clinical settings.
- Arthroscopy: This is a minimally invasive procedure that uses a tiny camera inside the knee to confirm ligament damage.
Treatment Options For ACL Tear
Managing an ACL tear involves various treatment options to support knee function and recovery. The best approach depends on the severity of the tear and the individual’s activity level.
- RICE method: The RICE method—rest, ice, compression, and elevation—helps reduce swelling but can slow healing, cause stiff joints, and lead to ice burns if overused.
- Physical therapy: Strengthening exercises improve flexibility, restore motion, and help prevent future injuries.
- Assistive devices: Knee braces or crutches provide support and minimize stress on the knee during healing.
Surgery Isn’t Always The Best Option — Here’s Why
Surgery is not always necessary for ACL injuries, and outcomes vary on the individual. Research shows that only about half of athletes who undergo ACL reconstruction regain full function and return to their previous level of sports. While surgery can help restore knee stability, it may not fully replicate the natural movement and sensory feedback (proprioception) of an intact ACL. Surgical intervention has its benefits, but it also carries risks. Reported complications include:
- Approximately 17% of adults will experience Anterior knee pain or pain when kneeling.
- Between 5% and 29% will experience graft failure and loss of knee joint stability, with higher rates in younger patients.
- Other potential complications include:
- Knee stiffness or loss of range of motion (approximately 5%)
- Painful hardware (approximately 6%)
- Infection (approximately 1% to 2%)
- Patellar tendon rupture or patellar fracture in the case of bone-to-bone grafts.
- Increased youth participation in high-intensity sports has led to more ACL surgeries, but research suggests complications may be worse in teens. A study of 160 clinical trials found higher post-surgery complications in young teens, with increased risks of growth disturbances, skeletal deformities, and ligament re-rupture requiring a second surgery.
- A 2010 Swedish study showed that 60% of athletes (average age: 26) who chose physical therapy over surgery didn’t need ACL reconstruction and were still able play sports.
Interventional Orthobiologics For ACL Tears
Interventional orthobiologics may offer a non-surgical option for ACL injuries. Physicians in the licensed Regenexx network use X-ray guidance to precisely inject bone marrow concentrate, processed with Regenexx lab protocols, into the affected area.
The cellular healing agents in bone marrow concentrate may support the body’s natural healing response, potentially helping to maintain knee stability and function. This approach offers an alternative to surgery, potentially reducing downtime and reliance on medications.
Perc-ACLR: Redefining Non-Surgical Ligament Care
Perc-ACLR (percutaneous ACL repair) is an approach developed by physicians in the licensed Regenexx network to address partial and select full-thickness non-retracted ACL tears without surgery. ACL injuries are among the most common knee issues, and this technique provides a minimally invasive alternative for many cases.
This innovative procedure uses precise image guidance to deliver orthobiologic injectates processed with Regenexx lab protocols, supporting the body’s natural healing response. By avoiding traditional surgery, Perc-ACLR may help patients maintain knee stability and function with fewer risks and less downtime.
Research shows that ACL sprains and select non-retracted ACL tears may improve over time, especially with interventional orthobiologic procedures like Perc-ACLR. These techniques activate the body’s natural healing response, offering a non-surgical alternative for many individuals.
Depending on the severity of the ACL injury and individual recovery goals, some patients may not need surgery. For those who do, the Perc-ACLR procedure can be performed in a single day by physicians in the licensed Regenexx network.
- A physician in the licensed Regenexx network extracts bone marrow using imaging guidance and a specialized Regenexx technique.
- The marrow is processed using Regenexx lab protocols while the patient rests for three to six hours.
- Local anesthesia is applied before reinjection to enhance comfort and minimize pain.
- Fluoroscopy, MRI, and X-ray contrast help guide precise injection into the damaged ligament.
Patients may experience mild soreness for one to three days, with discomfort usually decreasing within five to seven days. Most individuals may begin to notice improvement within a month and may be able to begin light activities and physical therapy.
Recovery Time Without Surgery
When considering recovery options, it’s important to evaluate the best approach for long-term knee health and a return to activity. The Regenexx approach focuses on preserving the ACL rather than replacing it. Research and clinical experience suggest that certain ACL injuries may improve through interventional orthobiologic techniques.
The Perc-ACLR procedure is a precise, X-ray-guided injection of a patient’s own bone marrow concentrate, completed in a single day. This approach is significantly less invasive than surgery. It typically involves shorter recovery times, potentially allowing for a faster return to activity. Individual results may vary.
| Perc-ACLR | Surgery | |
|---|---|---|
| Procedure Invasiveness | Much less | Much more |
| Return to Sports | 3 to 6 months | 1 year |
| Keep your ACL | Yes | NO |
| Recovery | Brace, much less extensive PT | Crutches, brace, extensive PT |
BEFORE And AFTER Procedure MRI Images
The before and after images show the outcomes of patients who opted for a procedure instead of ACL surgery.
In the before image, the ACL appears visibly torn. The after image shows a dark band running diagonally, suggesting structural changes in the ligament following the procedure. This comparison illustrates how non-surgical approaches may support the body’s natural healing response.
Explore Non-Surgical Options For Managing Your Knee Condition
The physicians in the licensed Regenexx network provide non-surgical options, such as Perc-ACLR, which use interventional orthobiologic techniques to support the body’s natural healing response. These minimally invasive treatments may provide an alternative to surgery, potentially reducing downtime.
Consulting with a healthcare professional is essential to determine the most appropriate treatment plan. Exploring the Regenexx approach may help individuals take a proactive approach to maintaining knee function and long-term mobility.
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