ACL Injury

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The anterior cruciate ligament, or ACL, is one of four major ligaments that make up the knee. Ligaments are in place to stabilize the femur (thigh bone), which sits just above the tibia (shin bone).

Description of ACL Injuries

The ACL is critical to maintaining knee stability. ACL injuries are very common among athletes of all ages and competitive levels. Approximately 200,000 ACL injuries are reported each year in the United States. Soccer, football, skiing, lacrosse and basketball are some common examples of higher-risk sports that see a high number of ACL injuries. In almost all sports, the rate of ACL tears is higher in women than in men.

Symptoms of an ACL Injury:

• Patients with an ACL tear often report instability in the knee and a
• Feeling as if it will “give out”, or pop out of place

More times than not, patients will opt to have ACL surgery to treat the injury because of the desire to resume contact or twisting sports, such as skiing. A large majority of ACL injuries—approximately 50 percent—occur in combination with an additional injury and damage to the meniscus, articular cartilage, or other ligaments.

In addition to role in providing stability, the ACL also provides protection for the menisci of the knee. When the knee continues to have instability episodes, it is not uncommon for the medial or lateral meniscus to tear. However, with the presence of a meniscal tear there is much higher risk of developing osteoarthritis. Because of this, Dr. LaPrade usually recommends ACL reconstruction for an ACL tear in young or otherwise active patients, in patients who have meniscal tears, and in almost all patients who report instability with twisting or turning activities.

Dr. LaPrade will evaluate the patient’s knee to determine if in fact an ACL tear has occurred through a series of clinical tests, x-rays and an MRI. The MRI will also determine if there is an injury associated with another knee ligament, the meniscus or articular cartilage.

In order to verify if the ACL is in fact still intact, Dr. LaPrade will perform the Lachman’s test. In a torn ACL, increased forward movement will be felt in relation to the tibia and femur. This will feel mushy and soft which is the result of an ACL tear. Other tests may also be used including the Pivot Shift Test to check for anterolateral instability of the knee.

Degrees of an ACL Injury:

• Grade I Injury: A Grade I injury of the ACL does not involve a tear, but instead, minor stretching of the ligament which may show up as swelling in the ligament on MRI. Patients will feel swelling and tenderness but will be able to resume normal activities for the most part.
• Grade II Injury: This injury represents a partially torn ACL (usually one of the two bundles) and is considered to be more serious. Inflammation will occur and soreness to the knee will be present. Walking for patients is usually more difficult. Surgery may be recommended.
• Grade III Injury: This injury occurs when the ACL is torn completely. Patients are usually in severe pain; inflammation and swelling will peak and walking without a limp will become difficult if not impossible.

How to Read a MRI of an ACL Tear

Treatment for an ACL Tear

For patients who experience a Grade II or Grade III ACL tear and who have a meniscus tear, there is a much higher risk for the development of osteoarthritis in the future. Because of this, Dr. LaPrade will usually recommend a combined meniscus repair and ACL reconstruction to be performed, and for ACL reconstructions to be performed in young or otherwise active patients and in almost all patients who report instability with twisting or turning activities.

The technique of ACL surgery has changed dramatically over the last decade in the orthopaedic (orthopedic) community. Anterior cruciate reconstruction grafts performed prior to 5-10 years ago were placed more centrally on both the tibia and femur – research has shown many of these patients have continued problems with rotation instability. This problem became recognized through extensive clinical and biomechanical research and the surgical technique has changed to where the reconstruction tunnels are now placed more anatomically to provide better stability to the knee. Dr. LaPrade’s research team has been instrumental in helping better define the anatomy that has lead to improved ACL reconstruction techniques.


It is absolutely essential for a well-supervised physical therapy protocol following ACL reconstruction surgery. Reactivation of the quadriceps mechanism, edema control, patella mobilization, maintenance of full knee extension and regaining knee motion are absolutely essential to obtaining optimal post-operative outcomes. Dr. LaPrade strongly suggests and requires patients to remain in Vail, Colorado to work with our physical therapists at Howard Head Sports Medicine for a minimum of 5-7 days post-operatively to ensure they are having proper care post-operatively and also so that their rehabilitation will advance to high levels at a quicker pace.

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