The
anterior cruciate ligament (
ACL) is one of the four major
ligamentIn anatomy, the term ligament is used to denote three different types of structures:# Fibrous tissue that connects bones to other bones. They are sometimes called "articular ligaments", "fibrous ligaments", or "true ligaments"....
s of the
humanHumans are bipedal primates belonging to the species Homo sapiens in Hominidae, the great ape family. They are the only surviving member of the genus Homo. Humans have a highly developed brain, capable of abstract reasoning, language, introspection, and problem solving...
kneeThe knee joint joins the thigh with the leg and consists of two articulations: one between the femur and tibia, and one between the femur and patella. It is the largest and most complicated joint in the human body. The knee is a mobile trocho-ginglymus , which permits flexion and extension as well...
. In the
quadrupedQuadrupedalism is a form of land animal locomotion using four limbs or legs. An animal or machine that usually moves in a quadrupedal manner is known as a quadruped, meaning "four feet"...
stifleThe stifle joint is a complex joint in the hind limbs of quadruped mammals such as the sheep, horse or dog. It is the equivalent joint to the human knee...
(analogous to the knee), based on its anatomical position, it is referred to as the
cranial cruciate ligament.
The ACL originates from deep within the notch of the distal femur. Its proximal fibers fan out along the medial wall of the lateral femoral condyle. There are two bundles of the ACL—the anteromedial and the posterolateral, named according to where the bundles insert into the tibial plateau.
The
anterior cruciate ligament (
ACL) is one of the four major
ligamentIn anatomy, the term ligament is used to denote three different types of structures:# Fibrous tissue that connects bones to other bones. They are sometimes called "articular ligaments", "fibrous ligaments", or "true ligaments"....
s of the
humanHumans are bipedal primates belonging to the species Homo sapiens in Hominidae, the great ape family. They are the only surviving member of the genus Homo. Humans have a highly developed brain, capable of abstract reasoning, language, introspection, and problem solving...
kneeThe knee joint joins the thigh with the leg and consists of two articulations: one between the femur and tibia, and one between the femur and patella. It is the largest and most complicated joint in the human body. The knee is a mobile trocho-ginglymus , which permits flexion and extension as well...
. In the
quadrupedQuadrupedalism is a form of land animal locomotion using four limbs or legs. An animal or machine that usually moves in a quadrupedal manner is known as a quadruped, meaning "four feet"...
stifleThe stifle joint is a complex joint in the hind limbs of quadruped mammals such as the sheep, horse or dog. It is the equivalent joint to the human knee...
(analogous to the knee), based on its anatomical position, it is referred to as the
cranial cruciate ligament.
The ACL originates from deep within the notch of the distal femur. Its proximal fibers fan out along the medial wall of the lateral femoral condyle. There are two bundles of the ACL—the anteromedial and the posterolateral, named according to where the bundles insert into the tibial plateau. The ACL attaches in front of the
intercondyloid eminence-Anatomy:Between the articular facets of the upper extremity of the tibia, but nearer the posterior than the anterior aspect of the bone, is the intercondyloid eminence , surmounted on either side by a prominent tubercle, on to the sides of which the articular facets are prolonged; in front of and...
of the tibia, being blended with the anterior horn of the
lateral meniscusThe lateral meniscus, also called the external semilunar fibrocartilage, is a fibrocartilaginous band that spans the lateral side of the interior of the knee joint. It is one of two menisci of the knee, the other being the medial meniscus. It is nearly circular and covers a larger portion of the...
. These attachments allow it to resist anterior translation of the tibia, in relation to the femur.
Anterior cruciate ligament injuryAn injury to the anterior cruciate ligament can be a debilitating musculoskeletal injury seen most often in athletes. Non-contact tears and ruptures are the most common causes of ACL injury.-Causes:...
is the most common knee ligament injury especially in athletes.
Causes of injury
The ACL is the most commonly injured knee ligament and is commonly damaged by athletes. The ACL is often torn during sudden dislocation, torsion, or hyperextension of the knee. Commonly patients report hearing or feeling a "pop", but many report minimal pain at the time of ACL rupture. In the hours following ACL rupture, however, most patients notice progressive swelling (usually due to bleeding of the vessels along the torn ACL). This swelling generally is quite painful, but can be minimized by icing the knee. ACL tears typically occur in sports where cutting, twisting, and turning are common, such as Skiing, Gymnastics, American Football, and Soccer.
The most common causes of ACL rupture can be divided into three major classifications:
- environmental
- anatomical
- hormonal
Environmental causes
Sports which include running and jumping pose the most potential for injury to the athlete. The risk for rupture of the anterior cruciate ligament does not increase in contact sports (as opposed to noncontact sports).
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.
Hormonal causes
High levels of specific hormones have been associated with an increased risk of ACL rupture.
EstrogenEstrogens are a group of steroid compounds, named for their importance in the estrous cycle, and functioning as the primary female sex hormone, their name comes from estrus/oistros + gen/gonos = to generate.Estrogens are used as part of some oral contraceptives, in estrogen replacement...
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.
Women and ACL tears
Statistics show that females are now more than 8 times as likely to tear their ACL than male athletes. Statistics also show that female athletes have a 25% chance of tearing their ACL a second time after having the reconstruction surgery done. Differences between the sexes in hormones, adolescence, ligament dominance and quadriceps dominance, biomechanics, anatomy, asymmetry, and psychology all may contribute to this anomaly.
Main Reason For Female ACL Tears
As a result of the increased angle formed by a woman's hips and her knees, the ligaments are constantly under more pressure than a man's.
Adolescents
Young girls aren't as likely to tear their ACLs as young women, because their hips have not widened more than a boy's of the same age. According to Anna Kessel, when puberty occurs this changes the risk of women tearing their ACL from 2 times to 4 times more than men.
Ligament and quadriceps dominance
Women's bodies tend to work in a way that uses the ligaments more than it uses muscles. When ligaments are compensating for muscles, it makes the ligaments weak and more susceptible to damage. Male athletes are more likely to use their hamstrings instead of their ligaments for stability. Instead of using their hamstrings, women tend to use their quadriceps, which compresses the joint and pulls the tibia forward. Doing this can cause damage or stress on the Anterior Cruciate Ligament. The quadriceps are made up of four muscles that help straighten the knee. When an athlete tears an ACL and has reconstruction surgery, the quadriceps are one of the most important muscles to strengthen at therapy.
Biomechanics
Women's bodies are shaped in a such a way that when they are jumping, pivoting, and landing, their knees are likely to bend inward. Doing so distributes the weight unevenly throughout the woman’s body. Scientists also suggest that the difference in men’s and women's femoral notch may be another reason women tear their ACL more often than men. The femoral notch - the space at the bottom of the femur, where the ACL runs - is narrower in women than in men. It is suggested that since the woman’s femoral notch is smaller, the femur grinds the ACL and can make it weaker. Another biomechanic that is said to likely cause ligament damage is the quadriceps femoris muscle angle, also known as the “Q-Angle”. The Q-Angle is larger in women's bodies than men's, because of their larger pelvises. The female’s ACL is shaped slightly differently than a male’s; it is also slightly smaller, according to Dr. Jonathan C. Cluett, M.D., a board certified orthopedic surgeon in Massachusetts, USA.
Diagnosis
Several diagnostic maneuvers help clinicians diagnose an injured ACL. In the
anterior drawer testThe anterior drawer test for anterior cruciate ligament laxity is one of many medical tests used to determine the integrity of the anterior cruciate ligament. It can be used to help diagnose sprain and tears....
, the examiner applies an anterior force on the proximal tibia with the knee in 90 degrees of flexion. The
Lachman testA Lachman test is a medical test used for examining the Anterior Cruciate Ligament in the knee for patients where there is a suspicion of a torn ACL...
is similar, but performed with the knee in only about twenty degrees of
flexionIn anatomy, flexion is a position that is made possible by the joint angle decreasing. The skeletal and muscular systems work together to move the joint into a "flexed" position. For example the elbow is flexed when the hand is brought closer to the shoulder...
, while the
pivot-shift testLateral Pivot Shift Test for Anterolateral Knee Instability This test can be use to look at the anterolateral structures’ of the knee and look for sprains of the different structures....
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
arthroscopiesArthroscopy is a minimally invasive surgical procedure in which an examination and sometimes treatment of damage of the interior of a joint is performed using an arthroscope, a type of endoscope that is inserted into the joint through a small incision...
performed.
Treatment options
Treatment for an ACL injury can either be nonsurgical or surgical depending on the extent of the injury.
Nonsurgical options may be used if the knee cartilage is undamaged, the knee proves to be stable during typical daily activities, and if the patient has no desire to ever again participate in high-risk activities (activities involving cutting, pivoting, or jumping). If the nonsurgical option is recommended, the doctor may recommend physical therapy, wearing a knee brace, or adapting some typical activities. If physical therapy is recommended it will be used to strengthen the muscles around the knee to compensate for the absence of a healthy ACL. Physical therapy will focus on strengthening muscles such as the hamstring, quadriceps, calf, hip, and ankle. This therapy will help to re-establish a full range of motion of the knee. With the use of these nonsurgical options a patient can expect to be back to normal daily activity within one month. However, most ACL-deficient athletes conclude that their knee continues to feel unstable, again confirming the important role of the ACL in normal knee stability.
Other non-surgical options include prolotherapy, which has been shown by Reeves in a small randomized controlled trial (among patients already suffering arthritis) to reduce translation on KT-1000 arthrometer versus placebo. This article may be of interest for those who are older, or have knee degeneration, but is not as applicable to the younger ACL-deficient patient who does not have arthritis of the knee. The future of non-surgical care for ACL laxity (partial ligament tear) is likely bioengineering. Fan has demonstrated that ACL reconstruction is possible using mesenchymal stem cells and a silk scaffold.
Surgical options may be used if the knee gives way during typical daily activities, showing functional instability, or if the patient is unable to refrain from participating in high-risk activities ever again. Reconstructive surgery may also be recommended if there is damage to the meniscus (cartilage). This surgery is completed using arthroscopic techniques. There is also an option for an autograft to be done using a chosen tendon. There are, however, pros and cons to the surgical treatment, and consideration of possible complications must be thought through and discussed with your surgeon before proceeding with this form of treatment. If the surgical treatment is chosen there are also rehabilitation requirements. Physical therapy must be completed in three phases after the surgery is completed. With the use of the surgical treatment option, rehabilitation included, a patient can expect to be returning to previous and desired levels of activity in six to nine months.
See also
- Lateral collateral ligament
- Medial collateral ligament
The medial collateral ligament of the knee is one of the four major ligaments of the knee. It is on the medial side of the knee joint in humans and other primates. It is also known as the tibial collateral ligament, or abbreviated as the MCL.- Structure :It is a broad, flat, membranous band,...
- Posterior cruciate ligament
The posterior cruciate ligament is one of the four major ligaments of the knee. It connects the posterior intercondylar area of the tibia to the medial condyle of the femur...
- Anterior drawer test
The anterior drawer test for anterior cruciate ligament laxity is one of many medical tests used to determine the integrity of the anterior cruciate ligament. It can be used to help diagnose sprain and tears....
- Anterior cruciate ligament reconstruction
Anterior cruciate ligament reconstruction is a surgical tissue graft replacement of the anterior cruciate ligament, located in the knee, to restore its function after anterior cruciate ligament injury. The torn ligament is removed from the knee before the graft is inserted through a hole created...
External links