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There are three bones that make up the knee joint – the femur or thigh bone, the tibia or shin bone, and the kneecap or patella. There are two cruciate ligaments inside the knee joint that form an X and control the backward and forward motion of the knee, as well as rotation.

What is the ACL?

The Anterior cruciate ligament (ACL) is one of a pair of cruciate ligaments that form the X. The ACL sits in front of the knee joint and the posterior cruciate ligament (PCL) in back.

How does the ACL work?

The purpose of the ACL ligament is to prevent the tibia (the shin bone) from sliding in front of the femur (the upper leg bone) and to stabilize the knee during rotation. The ACL ligament also contains important nerve fibers that can tell your brain where your knee is positioned in space during activities such as running and jumping.

How do injuries to the ACL occur?

Traumatic Injury to the ACL occurs in athletes who participate in high-risk sports such as skiing, soccer, football and basketball. Most ACL injuries result from a sharp twisting of the knee, sudden deceleration while cutting, pivoting, sidestepping movements, sudden stopping when running, and awkward landing from a jump. Other causes include direct contact, a fall or traumatic accident. Women who participate in college sports such as soccer, basketball, softball, lacrosse, rugby are approximately four times more likely than men to rupture their ACL.

What are the symptoms of an ACL injury?

When you injure your ACL, you may hear a popping sound at the time of injury coupled with buckling of the knee. There will be immediate and intense pain, swelling, inflammation, redness and bruising. The pain may resolve but the knee will typically remain unstable, with a loss of knee range of motion. Continuing to participate in sports or ACL dependent activities may cause more damage. Other symptoms may include tenderness on the inside or outside of the joint (if there is an associated meniscus tear), and buckling of the knee and difficulty with walking.

Can an ACL injury heal on its own?

Yes, some ACL injuries can heal without surgery, especially incomplete injuries. For complete tears of the ACL, conservative treatment can potentially be successful in patients who do not intend to return to pivoting activities. Patients whose goal is to return to high-risk sports and ACL dependent activities will be recommended for surgical reconstruction to restore stability of the knee and prevent progressive injury to the cartilage and meniscus.

Severity of ACL tears (rupture)

  • Grade 1 ACL Sprain: ACL injuries that stretch the ligament can heal on their own with conservative treatment: rest, ice, compression, elevation, and anti-inflammatory medications.
  • Grade 2 Partial ACL tears: ACL injuries that tear some of the ligament fibers are called “partial tears” and may heal with conservative management including physical therapy and bracing to return to low-demand sports and daily activities. Surgery to fix a partial tear will depend in part of the stability of the knee, and patient’s desire to return to the sport from which they were injured.
  • Grade 3 Complete ACL tears: A complete tear of the ACL is where the ligament is non-functional and requires surgery to reconstruct the ligament to provide knee stability during athletic activities.

What is the most accurate way to diagnose an ACL injury?

The combination of a detailed history, comprehensive physical examination, x-rays, and an MRI is the key to successful diagnosis of the integrity of the ACL. Because almost half of all ACL injuries occur in combination with other knee injuries imaging studies are important to evaluate the full extent of your injuries. In addition to image testing (MRI), Dr. Jorge Chahla use stability tests, as the Lachman and Anterior Drawer Tests to properly diagnose an ACL Injury.

What is the best time to fix an ACL injury?

Studies report that patients may benefit from beginning with physical therapy to strengthen the muscles surrounding the knee (pre-rehabilitation), mainly when range of motion is not optimal, followed by surgical reconstruction. Generally, delaying surgery until the pain, swelling and inflammation have decreased, and range of motion has been restored with physical therapy provides the best outcome. The timing of surgery is made on a case-by-case basis.

How is an ACL injury fixed?

Knee arthroscopy is a minimally invasive procedure employed to view, assess and treat a torn ACL. ACL reconstruction involves the replacement of the ruptured ligament with a tendon graft. Knee arthroscopy can also repair a torn meniscus commonly found with an ACL rupture. ACL reconstruction involves replacing the torn ACL with tissue taken from the patient (autograft) or taken from a tissue donor (allograft).

The source of the graft tissue and the technique depend on the severity of the injury, desired outcome and preferred method of the surgeon. Bone-patellar tendon-bone (BTB) autograft anterior cruciate ligament (ACL) reconstruction has the longest proven record of successful outcomes and is the technique by which all others are compared. Other options are the hamstring tendons (semitendinosus and gracilis) along the inside part of the thigh and knee. More recently, the quadriceps tendon has gained popularity for use as a graft source for ACL reconstruction, however, further data is necessary for a more generalized use.

How long is the recovery?

Recovery from an ACL reconstruction can take on average 6-9 months including full rehabilitation to restore range of motion, strengthen the muscles and recover balance. Furthermore, injury prevention after completing the rehabilitation is of utmost importance to prevent subsequent injuries.

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