An ACL injury is one of the most common knee injuries, and among the best known in sports. We hear the term often, but few know what the ACL is or how a torn ACL is treated

What is the ACL?

ACL stands for anterior cruciate ligament. It is one of four ligaments (bands of connective tissue) that connects the thigh bone (femur) to the shin bone (tibia) and supports the knee as it rotates. It is located at the center of the knee.

What are the most common ACL injuries?

When a ligament such as the ACL is injured, it can be overly stretched, partially torn (which is rare), or torn into two sections. It is estimated that there are about 400,000 ACL tears each year in the United States.

These injuries occur most often among athletes, especially those who must perform sudden changes in direction or abrupt starts and stops. Also, jobs that involve climbing or jumping are associated with ACL tears. It’s interesting to note that women who participate in sports that require quick direction changes such as soccer, lacrosse, and basketball are four times as likely to experience ACL tears than men, though the exact reason for that is not definitive. 

What causes ACL tears?

There are numerous ways an ACL tear can occur. “Non-contact” injuries usually happen when someone suddenly stops running or changes direction, or lands awkwardly from a jump. The ACL can also tear when the knee is involved in a contact injury during athletics or an accident.

Signs and symptoms of an ACL injury

There are several typical signs and symptoms that help identify an ACL tear, which may include:

  • a “popping” sound in your knee
  • feeling as if your knee will give out and not support you
  • pain, tenderness, discomfort when walking
  • swelling 
  • reduced range of motion

How are ACL injuries diagnosed?

Your doctor will examine your knees and compare one to the other, take a full medical history, and possibly order X-rays. Sometimes the exam itself is enough to confirm whether there is a tear to the ACL. However, an MRI is often ordered as this type of scan will clearly show whether the ligament is torn, as well other associated injuries.

What are the treatment options for ACL injuries?

Immediately following a tear to the ACL, you should use the “R.I.C.E.” method. That means:

  • Rest
  • Ice
  • Compression
  • Elevation

Treatment options for ACL tears may be non-surgical or surgical. You might be surprised to learn that treatment for ACL tears is often determined by the patient. Some athletes may opt for surgery to get them back to the game as soon as possible, while less active individuals may choose a more conservative approach.

Non-surgical treatment involves using a brace to support the knee and crutches to minimize weight-bearing on that leg, along with physical therapy.

Surgery to repair a torn ACL typically involves minimally invasive (arthroscopic) surgery. Your surgeon will use tiny instruments to graft a piece of tendon from another part of your body such as the hamstring to the torn ligament. This is followed by a period of physical therapy and strengthening exercises.

How long does recovery and rehab take after ACL surgery?

Following surgery, typical recovery time for full athletic return is six to nine months, with rehabilitation a key focus of your recovery. 

New surgical approach and research for ACL injuries

Orthopedic surgeons are now testing a new technique in surgical repair of ACL injuries known as BEAR (Bridge-Enhanced ACL Restortation). Rather than using a tendon from another part of the body to reconstruct the torn ACL, surgeons can now use a special device along with sutures and stitches to reconnect the ligament and allow it to heal itself. 

To determine the effectiveness of this new approach, there is currently a national clinical trial underway at six sites across the U.S. The BEAR-MOON study (Bridge-Enhanced ACL Restoration-Multicenter Orthopaedic Outcomes Network) will include adult participants with a torn ACL that has occurred within the past 50 days who qualify for surgery. 

Learn more about ACL injuries and the BEAR-MOON study

Brett D. Owens, MD

Dr. Brett Owens is a fellowship-trained, board-certified orthopedic sports medicine surgeon, specializing in arthroscopic repair of sports-related injuries as well as complex knee and shoulder reconstructions. He is a professor of orthopaedic surgery at The Warren Alpert Medical School at Brown University.