Anterior cruciate ligament
From Wikipedia, the free encyclopedia
| Ligament: Anterior cruciate ligament | ||
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| Diagram of the right knee. (Anterior cruciate ligament labeled at center left.) | ||
| Latin | ligamentum cruciatum anterius | |
| Gray's | subject #93 342 | |
| From | lateral condyle of the femur | |
| To | intercondyloid eminence of the tibia | |
| Dorlands/Elsevier | l_09/12492099 | |
The anterior cruciate ligament (or ACL) is one of the four major ligaments of the knee. It connects from a posterio-lateral part of the femur to an anterio-medial part of the tibia. These attachments allow it to resist anterior translation of the tibia, in relation to the femur. More specifically, it is attached to the depression in front of the intercondyloid eminence of the tibia, being blended with the anterior extremity of the lateral meniscus. It passes up, backward, and laterally, and is fixed into the medial and back part of the lateral condyle of the femur.
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[edit] Causes of Injury
The ACL is the most commonly injured knee ligament [1]) and is commonly damaged by athletes. The ACL is often torn during sudden dislocation, torsion, or hyperextension of the knee and is usually quite painful. It is a very common injury in football, hockey, lacrosse, skiing, skating, soccer, netball, Ultimate Frisbee and in less cases basketball, due to the enormous amount of pressure, weight, and torque the knee must withstand. Usually the injury occurs when someone tries to rapidly change direction with the leading leg out, twisting the knee. Or sudden high pressure contact, especially side on.
The known causes of ACL rupture can be divided into three major classifications:
- environmental
- anatomical
- hormonal [2]
[edit] Environmental Causes
Sports which include running, jumping, and landing pose the most potential for injury to the athlete. Interestingly, the risk for rupture of the anterior cruciate ligament does not increase in contact sports (as opposed to noncontact sports). According to Maureen Madden, a physical therapist working with many ACL rupture patients, "the most encouraging aspect of the bad news about ACL tears is that 70 (percent) are noncontact injuries." [3]
[edit] Anatomical Causes
ACL injuries are especially common in female athletes, due to many possible contributing factors. The most prevalent explanation relates to female athletes tending to land more straight-legged than men, removing the quadriceps' muscles shock-absorbing action on the knee. Often the knee on a straight leg can't withstand this and bends sideways.
[edit] Hormonal Causes
High levels of specific hormones have been associated with an increased risk of ACL rupture. Estrogen is one of these hormones. Some anatomical and hormonal causes (such as high levels of estrogen) may put women at a higher risk for injury. [2]
[edit] Injury in Females
Women are more susceptible to ACL rupture and new research shows that women may be up to 8 times more likely than men to rupture the ACL. Researchers continue to debate why women are more likely to tear their ACL than men. Most theories center on the "anatomical and hormonal differences among men and women." [3]A few of these differences include the following:
[edit] Hormonal Levels
According to Dr. Kurt Spinder, "Females have an increased frequency, or in other words a greater risk to tear their ACL at mid-cycle ovulation." [2] Spinder recently conducted a study focused on the stage of the menstrual cycle for 65 women with ACL injuries and his discovery may mean there is a correlation between a woman's hormones and her susceptibility to an ACL injury. Increased production of estrogen and other feminine hormones may cause a woman's motor skills to decrease and/or relax the ACL and surrounding ligaments.
[edit] Intercondylar Notch
The intercondylar notch is a small groove located at the end of the femur, directly behind the patellar tendon. The location of the notch makes it a prime suspect for damage to the ACL, which has prompted many studies. One recent study using cadavers showed that the ACL comes in contact with the intercondylar notch when the leg is fully extended. [4] The fact that the notch is generally narrower in women than in men may contribute to the higher rate of ACL injuries in women.
[edit] Hamstring and Quadricep balance
A third reason females are more susceptible to rupturing an ACL may be an imbalance between the quadriceps and hamstrings. The quadriceps and hamstrings are the muscles on the front and back of the thigh, around the femur. Many women have much stronger quadricep muscles than hamstrings, while men tend to have a more even distribution of muscle strength. This anatomical difference between men and women has led experts to believe it plays a role in knee stability. Doctors Boden, Griffin, and Garrett published this statement in "Etiology and Prevention of Noncontact ACL Injury" in a recent issue of The Physican and Sports Medicine:
The quadriceps, as ACL antagonists, may contribute to ACL injury. Numerous investigators have reported that quadriceps contraction increases ACL strain between 10º and 30º of knee flexion. Because most noncontact ACL injuries occur with the knee close to full extension, it is possible that the quadriceps play an important role in ACL disruption...According to mechanical calculations, an eccentric quadriceps muscle contraction can produce forces beyond those required for ACL tensile failure.
Hamstrings clearly play an important role in supporting the ACL. Thus, both men and women with weak hamstrings and strong quadriceps are at higher risk for an ACL tear.
[edit] Posture
A final reason women are more likely to tear an ACL may be running and jumping posture. Since many ACL injuries are noncontact and occur while athletes are stopping, turning, running, and jumping, researchers have paid close attention to differences in men and women while exercising. Hundreds of studies have been conducted and show women tend to run in a more upright position than men, which may increase the stress on the ACL. Although the concept of posture increasing the risk for ACL injury is generally accepted in the medical community, it is important to note there is no conclusive evidence showing why the upright position is more dangerous. As research continues, more evidence can be gathered and more factors that increase the risk of ACL damage will, undoubtedly, be uncovered.
[edit] Diagnosis
Several diagnostic maneuvers help clinicians diagnose an injured ACL. In the anterior drawer test, the examiner applies an anterior force on the proximal tibia with the knee in 90 degrees of flexion. The Lachman test is similar, but performed with the knee in only about twenty degrees of flexion, while the pivot-shift test adds a valgus (outside-in) force to the knee while it is moved from flexion to extension. Any abnormal motion in these maneuvers suggests a tear.
The diagnosis is usually confirmed by MRI, the availability of which has greatly lessened the number of purely diagnostic arthroscopies performed.
[edit] References
- ^ Widuchowski, Widuchowski, Widuchowski (2007). "Articular cartilage defects: Study of 25,124 knee arthroscopies". PMID 17428666.
- ^ a b c Coggin, Amber.. "ACL Study Links Injury to Menstrual Cycle." The Reporter. 2 Feb. 2005. Vanderbilt Medical Center..
- ^ a b Madden, Maureen.. "Women and ACL Injuries: Taking the Bad News with the Good." The Stone Clinic..
- ^ Boden, Barry MD, Letha Y. Griffin MD, and William E. Garret, Jr MD.. "Etiology and Prevention of Noncontact ACL Injury" The Physician and Sports Medicine.
[edit] See also
- Knee
- Lateral collateral ligament
- Medial collateral ligament
- Posterior cruciate ligament
- Anterior drawer test
- Anterior cruciate ligament reconstruction
[edit] Additional images
 Right knee-joint, from the front, showing interior ligaments. |
 Left knee-joint from behind, showing interior ligaments. |
 Head of right tibia seen from above, showing menisci and attachments of ligaments. |
 Capsule of right knee-joint (distended). Posterior aspect. |
[edit] External links
- The KNEEguru - educational site packed with knee content with sections on Anterior Cruciate Ligament (ACL)
- Anterior Cruciate Ligament (ACL) Reconstruction
- SUNY Labs 17:02-0701 - "Major Joints of the Lower Extremity: Knee Joint"
- SUNY Figs 17:07-08 - "Superior view of the tibia."
- SUNY Figs 17:08-03 - "Medial and lateral views of the knee joint and cruciate ligaments."
- Anterior+cruciate+ligament at eMedicine Dictionary
- Mnemonic at medicalmnemonics.com 2081
- Norman/Georgetown lljoints (antkneejointopenflexed)
- Anterior Cruciate Ligament Repair - Series (University of Maryland)
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