Anterior Cruciate Ligament Tear or ACL Tear

Knee diagram - anterior cruciate ligament tear

What is an ACL Tear?

Athletes who participate in high demand sports such as skiing, soccer, football, and basketball are more likely to injure their anterior cruciate ligaments. This is known as an anterior cruciate ligament tear or ACL tear. According to the American Academy of Orthopaedic Surgeons, “in the United States, around 200,000 ACL injuries occur each year.” Research also shows that the mean age of patients remains 29 years old, however, patients older than 40 and younger than 14 years old have seen a 200% increase in ACL tear surgery. This reflects the activity level and expectations of older and younger athletes. In most cases, ACL injuries can be treated successfully, allowing patients to return to an active lifestyle.

Understanding Your ACL and ACL Tears

What is the ACL?

Your ACL is one of the four major ligaments in your knee joint. It plays a critical role in stabilizing your knee and preventing the shinbone from sliding forward excessively. ACL tears can occur with sudden changes in direction, pivoting movements, landing from a jump incorrectly, or direct impact to the knee, which is why they are common sports injuries. The knee is the largest and most complex joint in the human body, essential for walking, running, and other fundamental movements.The femur, tibia, and patella are the bones that form the knee joint, while cartilage enables gliding movement and menisci act as shock absorbers and stabilize the joint. The tendons connect the bones and muscles. The four ligaments in the knee are: 
  • Anterior cruciate ligament (ACL): Prevents the shinbone from sliding forward excessively.
  • Posterior cruciate ligament (PCL): Prevents the shinbone from moving backward excessively.
  • Medial collateral ligament (MCL): Stabilizes the inner side of the knee and prevents outward bowing.
  • Lateral collateral ligament (LCL): Stabilizes the outer side of the knee and prevents inward bowing.

How and Why Do ACL Tears Happen?

When the ACL tears, it is typically quite traumatic, necessitating a stop to the game or a ski patrol ride to the base of the mountain. You may feel a pop with acute pain. Then you might feel unstable, like you cannot bear weight, followed by swelling. You initially treat this injury with physical therapy, rest, and ice.  You can also injure your ACL during a twisting non-contact event. Or, it may happen secondary to a contact injury where the knee is hit on the lateral or posterior side. Many ACL injuries occur in cutting sports such as basketball, soccer, and lacrosse, as well as skiing. ACL tears can be classified into three grades based on the severity of the damage:
  • Grade 1: A mild tear with some stretching of the ligament, still providing some stability.
  • Grade 2: A partial tear with significant instability and decreased function.
  • Grade 3: A complete tear where the ligament is fully ruptured, causing severe instability and inability to bear weight.
You may have been told that you have a partial or complete ACL tear. The differences are primarily in terms of severity, function, and treatment. A complete tear almost always requires ACL tear surgery to reconstruct the torn ACL and restore stability, as well as physical therapy to achieve full recovery.

Symptoms of an ACL Tear

You might hear a popping or tearing  sound at the time of the injury, especially during a sudden change in direction or landing from a jump. Sudden and intense pain in the knee joint is another common symptom, often described as a “stabbing” or “tearing” sensation. The knee joint will frequently swell significantly in the first few hours after the injury, which may cause a feeling of tightness or pressure. In addition, you may have difficulty putting weight on the injured leg and feel like your knee is buckling. You may have difficulty bending or straightening the knee fully due to pain and joint instability, and it may be painful to touch or apply pressure to the knee, especially at the joint. Some patients may experience bruising around the knee within a few days of the injury.  

Diagnosing an ACL Tear

Your doctor will discuss your symptoms, how the injury occurred, and previous knee problems, performing an examination of the knee to check for swelling, tenderness, range of motion, and instability.  Specific tests to assess ACL functionality include:
  • Lachman test: checks for excessive forward movement of the shinbone relative to the thigh bone.
  • Pivot shift test: assesses for abnormal looseness of the knee when pivoting.
  • Anterior drawer test: checks for excessive forward movement of the tibia when the knee is bent.
You’ll also probably have imaging tests, including X-rays to rule out bone fractures and magnetic resonance imaging (MRI) to get detailed images of your ligaments and tendons. An MRI is effective for diagnosis of an ACL tear, its severity, and any associated meniscal or cartilage injuries.

Treatment Options for an ACL Tear

When Is ACL Tear Surgery Recommended

The main reason to have ACL tear surgery is to restore stability to the knee, but it also protects the articular cartilage in the knee from being damaged. Protecting the medial and lateral menisci in the knee is also important. There are nonsurgical treatments, including physical therapy, modification of activity, and using a brace. You can strengthen the muscles around the knee (particularly the hamstrings) to compensate for losing the ACL. Many people can jog, cycle, and swim without surgical treatment. In some cases, using a brace is effective as well.  The decision to undergo ACL tear surgery depends on the severity of the tear, your activity level, your age, and your individual goals. In most cases, an orthopedic surgeon will recommend surgery for complete ACL tears to restore stability and prevent damage to the menisci, cartilage, and other ligaments. If the knee remains significantly unstable after a partial tear, and it affects your ability to perform everyday activities or participate in desired sports, you may want to have ACL tear surgery. Patients with active lifestyles, particularly those active in cutting sports, may seek surgery to regain full knee stability and safely return to their desired activities. While younger people may heal faster and have higher activity demands, age alone isn’t necessarily a precluding factor. Older individuals with active lifestyles or long-term health goals, may consider surgery to repair the ACL as well.

Surgical Options for ACL Repair

There are many surgical options for ACL repair, including ACL Tear Reconstruction with Autograft, ACL Tear Reconstruction with Allograft, and ACL repair with a BEAR IMPLANT. Options are changing  as we continue to conduct research and new options become available.  Occasionally, I have a patient whose primary goal is to run and cycle; these patients may only require non-operative treatment. However, the vast majority of people with ACL tears opt for surgical intervention. This arthroscopic procedure drills tunnels through both the femur (thigh bone) and tibia (shin bone) in order to pass a tendon through the center of the knee. Patients can choose the type of graft used to reconstruct the ACL. For young, high demand athletes, I recommend using their own hamstring or Quad tendon. For less active or slightly older patients, I prefer the relatively less invasive allograft/cadaver tissue option.

Recovery and Rehabilitation

Patients who have ACL tear surgery may begin riding a stationary bicycle less than one week following the surgery. You can begin walking and using crutches immediately after surgery. As you get stronger, you can use just one crutch and then none, when you can tolerate it.

Physical Therapy

After an ACL tear surgery, patients need physical therapy for 4 to 6 months.  It is important to exercise the knee regularly for a significant period of time after the procedure, and a physical therapist can help you make sure you are doing the right exercises safely and increase your activities as you grow stronger. 

Continuous Passive Motion Therapy

Continuous passive motion (CPM) machines generally are not used anymore after this surgery. We encourage patients to move their knees immediately after surgery.

How Long Does Recovery Take?

Generally, it takes within six to nine months to fully rehabilitate your knee after ACL tear reconstruction surgery. The goal is to give the new ligament time to develop a new blood supply and become strong before you return to high-velocity contact sports.

ACL Tears and Repair

Before you get surgery for an ACL tear, consider your overall health, because existing medical conditions or limitations can influence the surgical decision and recovery process. In some cases, physical therapy and bracing may be sufficient to manage symptoms and maintain stability. You should also consider the recovery time and commitment to physical therapy to regain full function. In the end, you should make the decision to undergo ACL tear surgery in consultation with an orthopedic surgeon who has the knowledge and expertise to provide guidance based on your specific situation. Make sure you understand the benefits and risks of surgery as compared to non-surgical approaches.