Anterior Cruciate Ligament Injury
The anterior cruciate ligament (ACL) lies in the middle of the knee, connecting the upper leg bone (femur) to the lower leg bone (tibia). In conjunction with the other 3 ligaments of the knee (medial collateral, lateral collateral and posterior cruciate) and the 2 meniscus cartilages (medial and lateral), the ACL proves overall stability to the knee and prevents joint wear and arthritis.
Studies have shown that women are three to four times more likely to injure their ACL than men. The factors that put women at an increased risk of an ACL injury include: wider hips which can lead to being knock-kneed, increased levels of estrogen which is believed to decrease the strength of the ligament and an imbalance between the quadriceps and hamstring muscles.
Due to its unique anatomy and location within the joint, the ACL will not heal back together once it is torn. Unfortunately, the torn ACL cannot be “sewn back together” with any technique that will restore its normal strength and function. In some cases non-surgical treatment is an option. However, there are very good surgical options for treatment that should allow you to return to participation in those activities and sports that you enjoyed prior to your ACL tear.
DIAGNOSIS OF AN ACL TEAR
Diagnosis is determined by your history, clinical exam with your physician (find a physician) and a MRI scan. The MRI scan will confirm the suspected tear and may show if other knee structures are damaged; such as other ligaments, meniscus cartilages or articular cartilage on the end of the bone.
SYMPTOMS: At the time of a fresh tear of the ACL ligament, a “pop” or “snap” is frequently heard. A sensation of the knee shifting out of place may be felt and swelling usually develops within 3 to 6 hours. Pain can vary from mild to a searing type of pain, most often felt on the outside, back corner of the knee. For ACL tears that go undetected or untreated, individuals tend to experience increased pain with each re-injury.
For the chronic or undetected ACL tear, one of ten people experiences a sensation of the knee giving way or shifting with rotational movements. This is most likely to occur when the foot is planted and the upper body rotates and changes direction. Popping, clicking and locking may be present and swelling may develop after physical activity.
Types of stresses that cause the ACL to tear:
1. Rotational Force
2. Rotation-Deceleration Force
3. Collision Force
What happens to the knee without an intact ACL?
Historical perspective: Long-term studies of knees without an anterior cruciate ligament show a predictable pattern of joint damage and premature wear. This leads to arthritic damage of the joint that is irreversible and will lead to permanent restrictions of activity and chronic pain. The time frame for this to develop is between 5 and 15 years in people who remain athletically active on their knee without the ACL being reconstructed.
Type of joint damage: In the freshly torn ACL knee, approximately one-third of knees will have an accompanying torn meniscus cartilage. If the ACL tear remains untreated, 90% of knees will have a torn meniscus cartilage by 5 years post injury.
Knees with untreated torn meniscus cartilages will have accelerated wear and damage to the articular cartilage (cartilage layer covering the ends of the thigh or leg bones). Articular cartilage damage frequently occurs with the shifting episode of an acute ACL tear. Recurring episodes of the knee shifting out of place almost always lead to articular cartilage damage. A divot in the cartilage develops, exposing the underlying bone.
With recurring episodes of the knee shifting out of place, damage to the other 3 ligaments can occur, causing them to stretch out and the knee becomes progressively unstable. In order to restore stability to the knee and to limit the premature joint damage and arthritic knee from developing, surgical reconstruction of the ACL is advised in the young and middle-aged individual.
