Where does the ACL attach to the femoral intercondylar?
In the anterior portion of the ACL, approximately 5–10 mm proximal to the tibial attachment, a layer of dense fibrous tissue surrounds the ligament instead of synovial tissue. This area corresponds to the zone where the ligament impinges on the anterior rim of the femoral intercondylar fossa in full knee extension.
What is the anterior cruciate ligament (ACL)?
The anterior cruciate ligament (ACL) is a band of dense connective tissue which courses from the femur to the tibia. The ACL is a key structure in the knee joint, as it resists anterior tibial translation and rotational loads.
What does the ACL do to the tibia?
The ACL resists anterior translation of the tibia relative to the femur; it also resists rotation. The cruciate ligaments are named according to their attachment on the tibia: the ACL courses from the posterior aspect of the intercondylar notch on the femur and inserts on the anterior tibial plateau.
Where does the ACL arise?
The ACL arises from the anteromedial aspect of the intercondylar area on the tibial plateau and passes upwards and backwards to attach to the posteromedial aspect of the lateral femoral condyle. Like the posterior cruciate ligament, the ACL is intracapsular but extrasynovial. The ACL consists of two components 4:
What bone is the ACL attached to?
The anterior cruciate ligament (ACL) is one of the ligaments in the knee joint. A ligament is a tough, flexible band of tissue that holds bones and cartilage together. The ACL connects the bottom of the thighbone (femur) to the top of the shinbone (tibia).
Where on the tibia does the ACL attach?
intercondylar notchThe anterior cruciate ligament (ACL) attaches from the anterior tibia (shin bone) to the femoral (thigh bone) intercondylar notch. As seen on the diagram, it lies just anterior to (in front of) the posterior cruciate ligament (PCL).
Where does PCL attach on femur?
tibial plateauThe PCL originates from the anterolateral aspect of the medial femoral condyle within the notch and inserts along the posterior aspect of the tibial plateau, approximately 1 cm distal to the joint line.
Can you bend knee with ACL tear?
Some people find that the knee joint feels looser than it should. Less range of motion. After you damage your ACL, it's very likely that you won't be able to bend and flex your knee like you normally would.
Where does a torn ACL hurt?
If you tear your ACL, it's probably going to hurt. Some people only feel mild pain. But in many cases, an ACL tear is going to hurt a lot. You'll typically feel the pain coming from the center of your knee.
Where do the ACL and PCL attach?
The PCL and ACL are intracapsular ligaments because they lie deep within the knee joint. They are both isolated from the fluid-filled synovial cavity, with the synovial membrane wrapped around them. The PCL gets its name by attaching to the posterior portion of the tibia.
What movement does the ACL limit?
The ACL stabilizes knee movement in a forward and backward direction. Specifically, the ACL prevents the tibia from sliding or twisting abnormally on the femur when the leg is straight or slightly bent. And the ACL prevents the knee from being stretched or straightened beyond its normal limits (hyperextended).
Which is longer ACL or PCL?
The PCL has an average length of 38 mm and an average width of 13 mm. The cross-sectional area of the PCL is variable and increases from tibial to femoral insertions. It is approximately 50% larger than the ACL at its femoral origin and 20% larger than the ACL at its tibial insertion.
Where does the ACL originate and insert?
The anterior cruciate ligament originates at the medial wall of the lateral femoral condyle and inserts into the middle of the intercondylar area. It contributes significantly to the stabilization and kinematics of the knee joint.
What is the tibial collateral ligament?
The tibial collateral ligament is also known as the medial collateral ligament (Video) or MCL. It is a ligament located along the inside of your knee that connects the femur (thighbone) to your tibia (shinbone). The knee relies on ligaments, which connect bone to bone, and surrounding muscles for stability.
What is ACL anatomy?
The anterior cruciate ligament (ACL) is a band of dense connective tissue which courses from the femur to the tibia. The ACL is a key structure in the knee joint, as it resists anterior tibial translation and rotational loads.
What excessive movement does the ACL prevent?
During activity, the ACL controls how far forward the tibia can "slide" relative to the femur: it essentially acts to prevent too much forward movement.
Where is the ACL attached to the tibial spine?
Tibial Attachment. The ACL is attached to a fossa in front of and lateral to the anterior tibial spine. At this attachment, the ACL passes beneath the transverse meniscal ligament, and a few fascicles of the ACL may blend with the anterior attachment of the lateral meniscus.
Where are the fibroblasts located in the ACL?
The fibroblasts, located on either side of the collagenous bundles are round to ovoid and resemble the cells of articular cartilage. In the anterior portion of the ACL, approximately 5–10 mm proximal to the tibial attachment, a layer of dense fibrous tissue surrounds the ligament instead of synovial tissue.
What is the femoral origin and tibial insertion?
The femoral origin and tibial insertion have the structure of a chondral apophyseal enthesis consisting of four layers. The first layer is composed of the ligament fibres. Fibro-cartilaginous cells aligned within the collagen bundles can be found in the second layer described as the non-mineralised cartilage zone, while the third layer is the mineralised cartilage zone. The fibrocartilage is mineralised and inserts into the subchondral bone plate, which is the fourth layer. Due to this specific anatomy of the insertions, the ACL shows a transition zone from rigid bone to ligamentous tissue thereby allowing a graduated change in stiffness and may prevent stress concentration at the attachment site.
What is the difference between ACL and PLB?
These fascicles have been summarily divided into two groups; the anteromedial band (AMB), those fascicles originating at the proximal aspect of the femoral attachment and inserting at the anteromedial aspect of the tibial attachment, and the posterolateral bulk (PLB), the remaining bulk of fascicles, which are inserted at the posterolateral aspect of the tibial attachment. In the frontal plane, the AMB has a more vertical orientation (approximately 70° to the knee baseline) while the PLB is oriented more horizontally (approximately 55° to the knee baseline). When the knee is extended the PLB is tight, while the AMB is moderately lax. However, as the knee is flexed, the femoral attachment of the ACL assumes a more horizontal orientation, causing the AMB to tighten and the PLB to loosen and thus leave the AMB as the restraint to anterior tibial load. Internal rotation lengthens the ACL a little more than does external rotation, most noticeably at 30° of flexion. Furthermore, Markolf et al. reported that ACL acts as a secondary restraint to varus-valgus angulation at full extension. Twisting is resisted by a combination of capsular shearing, slanting collateral ligament action, joint surface, and meniscal geometry, while the cruciate play only a secondary role.
What is the early manifestation of the ACL with two different bundles in the foetal knee?
The early manifestation of the ACL with two different bundles in the foetal knee suggests early development of the knee joint is guided by the ACL. Cruciate ligaments present at this early stage of development could lead to the assumption that they interact with the resulting shape of the femoral condyles and the tibial plateau.
How long does it take for a BPTB graft to change to a normal ACL?
Recently, Zaffagnini et al. performed a qualitative and quantitative histological evaluation, by transmission electron microscopy (TEM), of the neoligamentisation process of an autologous bone-patellar tendon-bone (BTPB) graft used as pro-ACL at different follow-up times. Their results showed that up to 24 months follow-up, progressive ultrastructural changes towards the normal ACL are observed. At longer times after surgery (48 and 120 months) no further changes were evident and the ultrastructure showed a marked reduction in large fibrils, which was typical of the control patellar tendon, and a significant increase in small fibrils. The ultrastructure seemed to combine fibrils from two different morphological units. The BPTB graft used as ACL underwent a transformation process for up to two years. After that period the transformation ceased and for ten years failed to reach the ultrastructural aspect of a normal ACL. However, from an architectural point of view the graft slowly transformed into a structure similar to ACL with respect to the different mechanical stresses the ligament has to sustain. A similar study with autologous hamstring graft is in progress.
How much stress does the ACL have?
divided the human ACL ligament into portions and tested the individual units for average modulus and ultimate tensile strength. The average modulus and ultimate tensile strength measured 278 and 35 MPa, respectively. The ligaments reached their ultimate stress at -15% strain. In a later study, Butler et al. found that AMB exhibited a larger modulus, ultimate tensile strength, and strain energy density than the posterior portion.
What is the function of the ACL?
The primary function of the ACL is to limit anterior translation (forward sliding) of the tibia on the femur in the knee joint. It secondarily aids in limiting the pivot of the knee joint. It has two bundles: an anteromedial (AM) and posterolateral (PL) bundle. The anteromedial bundle is tight in flexion (knee bending) and the posterolateral bundle is tight in extension (knee straightening). Recent evidence has shown that the AM bundle may play a large role in anterior-posterior translation (front to back motion) of the knee, and the PL bundle in rotational stability.
Where is the anterior cruciate ligament located?
The anterior cruciate ligament (ACL) attaches from the anterior tibia (shin bone) to the femoral (thigh bone) intercondylar notch. As seen on the diagram, it lies just anterior to (in front of) the posterior cruciate ligament (PCL). Both ligaments are named based on their insertion site on the tibia. On the femoral side, it attaches to the posteromedial aspect of the lateral femoral condyle. The average length is 33 mm (1.3 inches) and the width is 11 mm ( 0.43 inches). The anatomy and footprint of the ligament are very important in reconstruction.
How common are ACL injuries?
Anterior cruciate ligament (ACL) injuries are among the most common sports injuries in America. Close to 200,000 reconstructions are performed annually.
How can you diagnose an ACL tear?
ACL tears are often diagnosed based on history and physical exam. During a physical exam, the Lachman or Anterior Drawer test is performed. If your tibia slides anteriorly during these tests more than 1 cm without a solid end-point, then the test is positive and it’s most likely an ACL tear. Other physical exam tests include a knee arthrometer which can measure the side to side difference in the anterior translation of the tibia.
What is anatomic ACL reconstruction?
(Hatayama et al. 2013)* The latest evidence suggests that the best outcomes for success are anatomic ACL reconstruction where the patient’s anatomy is restored. (Fu et al. 2014)* (Porter and Shadbolt 2014)*
Can an X-ray show ACL tear?
X-rays are not able to diagnose an ACL tear except for a “Segond fracture” which is the avulsion of the anterolateral ligament. This may appear as a fleck of bone on the lateral (outside aspect) of your knee. The anterolateral ligament is an additional injured ligament which often signifies an ACL tear.
Can you play soccer without an ACL?
In general, without a functional ACL, patients should not participate in cutting-sports where side-to-side movements are done with the knee. These sports include but are not limited to soccer, tennis, baseball, basketball, and football. Though the body tries to adapt to ACL deficiency, it is not able to overcome it. (Takeda et al. 2014)* If you are able to safely undergo physical rehabilitation and you do not wish to return to cutting-sports, then you don’t need to have your ACL reconstructed. However, even if you don’t wish to return to cutting sports, and your knee remains unstable, then surgery would be necessary. (Dawson, Hutchison, and Sutherland 2014)*
What is the ACL in the right knee?
Diagram of the right knee. Anterior cruciate ligament labeled at center left. The anterior cruciate ligament ( ACL) is one of a pair of cruciate ligaments (the other being the posterior cruciate ligament) in the human knee. The two ligaments are also called "cruciform" ligaments, as they are arranged in a crossed formation.
Where does the ACL originate?
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. The two bundles of the ACL are the anteromedial and the posterolateral, named according to where the bundles insert into the tibial plateau. The tibial plateau is a critical weight-bearing region on the upper extremity of the tibia. The ACL attaches in front of the intercondyloid eminence of the tibia, where it blends with the anterior horn of the medial meniscus .
Why is the ACL called the Cruciate?
The term cruciate translates to cross. This name is fitting because the ACL crosses the posterior cruciate ligament to form an “X”. It is composed of strong, fibrous material and assists in controlling excessive motion. This is done by limiting mobility of the joint.
What is the purpose of the ACL?
Purpose. The purpose of the ACL is to resist the motions of anterior tibial translation and internal tibial rotation; this is important to have rotational stability. This function prevents anterior tibial subluxation of the lateral and medial tibiofemoral joints, which is important for the pivot-shift phenomenon.
What are the factors that affect the risk of ACL injury?
Risk differences between outcomes in men and women can be attributed to a combination of multiple factors, including anatomical, hormonal, genetic, positional, neuromuscular, and environmental factors. The size of the anterior cruciate ligament is often the most reported difference.
What is the most common knee injury?
Main article: Anterior cruciate ligament injury. An ACL tear is one of the most common knee injuries, with over 100,000 tears occurring annually in the US. Most ACL tears are a result of a non-contact mechanism such as a sudden change in a direction causing the knee to rotate inward.
What is anterior cruciate ligament surgery?
Anterior cruciate ligament surgery is a complex operation that requires expertise in the field of orthopedic and sports medicine. Many factors should be considered when discussing surgery, including the athlete's level of competition, age, previous knee injury, other injuries sustained, leg alignment, and graft choice.
What is the function of the ACL?
During activity, the ACL controls how far forward the tibia can "slide" relative to the femur: it essentially acts to prevent too much forward movement. While some degree of motion or sliding is normal and is required for knee function, too much motion may damage other structures in the knee which can lead to long term problems in some patients.
How is the ACL injured? What are the symptoms?
The ACL can be injured or torn in a number of different ways. The most common mechanism is that of a sudden pivoting or cutting maneuver during sporting activity , which is commonly seen in football, basketball and soccer. The ligament can also tear due to work injuries or automobile accidents.
How is an ACL injury diagnosed?
An ACL tear can be diagnosed by a physician through a history and physical examination. On physical examination, the physician can specifically assess the amount of motion present and determine if the ACL is torn. Additionally, evaluation of other structures within the knee is done also, as ACL tears are often found in association with injury to other structures within the knee, such as the cartilage and collateral ligaments.
What is the anterior cruciate ligament?
There is a ligament on each side of the knee (the collateral ligaments) and two ligaments deep inside the knee. The two ligaments inside the knee that “cross” each other are called the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL). Both ligaments attach on one side to the end of the thighbone (femur) and on the other to the top of the shinbone (tibia). [Figure 1].
How to tell if you have an ACL tear?
What are the symptoms of an ACL injury or tear? 1 A “pop” in the knee at the time of injury 2 Swelling of the knee 3 Inability to bear weight on leg (though some have little or no pain) 4 Instability of the knee
Why do you need a knee scan for ACL tear?
The scan is also useful for evaluating the cartilage or meniscus tissue in the knee if this information is necessary to make decisions regarding the best treatment for a specific patient.
Which ligaments attach to the thighbone?
The two ligaments inside the knee that “cross” each other are called the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL). Both ligaments attach on one side to the end of the thighbone (femur) and on the other to the top of the shinbone (tibia). [Figure 1].
How do hamstrings protect the ACL?
The hamstrings protect the ACL from tearing by countervailing the force that would otherwise exceed the ligament’s strength. The hamstrings (effectively) insert on the posterior tibia, and when the hamstrings contract, they flex the knee joint. (The word ‘effectively’ must be added, as only the semimembranosus itself inserts there.
How do ACL tears occur?
Tears of the ACL occur when the tibia goes one direction and the femur goes in another and the distance between the origin of the ACL on the femur and its insertion on the tibia exceeds the length of the ligament. Indeed, that ‘exceeded the distance’ mechanism is how all ligament tears occur.
What is the ligament that connects the femur to the tibia?
The anterior cruciate ligament (ACL) connects the femur to the tibia and stabilize the knee join. The ACL resists anterior translation of the tibia relative to the femur; it also resists rotation.
Why do hamstrings insert on the posterior tibia?
Because the hamstrings effectively insert on the posterior tibia, the firing of these muscles create a posterior-directed vector (see Figure 4). This vector of course resists anterior translation of the tibia. Because the hamstrings are likely very tired after 2pm, at this point they offer less resistance to anterior tibial displacement. Hence, a given force that would not lead to injury earlier in the day (when the hamstrings are strong) very well might later in the day.
Which ligaments are vertical?
Figure 2: A lateral view showing the anterior (green) and posterior (red) cruciate ligaments. Note the ligaments are mostly vertical; this orientation is suboptimal for resisting anterior/posterior translation but allows the knee to flex and extend more freely than a purely horizontal orientation would allow. Note also that the ACL inserts on the top of the tibia (the plateau) whereas the PCL inserts about 1 cm below the joint line.
What is the root word for cruciate ligaments?
The term “cruciate” refers to the fact that these ligaments cross each other (see Figures 1, 2 and 3). (The root word is ‘crus’ meaning ‘cross’. The term “excruciating” refers to pain likened to the suffering of crucifixion.)
Can you see the ACL and PCL simultaneously on MRI?
Because the ACL courses lateral (femur) to medial (tibia) and the PCL courses medial to lateral, it is rare to see both ligaments simultaneously on one single MRI image (Case courtesy of Dr. Andrew Dixon, https://radiopaedia.org/images/20228493)
What is the angle of the ACL?
The ACL Blumensaat line angle is normally ≤15º. It is calculated by drawing a line parallel to the roof of the intercondylar notch of the femur ( Blumensaat line ) and one parallel to the distal portion of the anterior cruciate ligament. The angle is calculated at the intersection of these two lines. An angle of >15º indicates an abnormal course and probable anterior cruciate ligament tear 3.
Where does the anterior cruciate ligament attach to?
The anterior cruciate ligament arises from the anteromedial aspect of the intercondylar area on the tibial plateau and passes upwards and backwards to attach to the posteromedial aspect of the lateral femoral condyle.
What is the function of the ACL?
The ACL functions to prevent posterior translation of the femur on the tibia (or anterior displacement of the tibia) during flexion-extension of the knee. The anteromedial bundle is responsible for the posterior translation of the femur at 30 degrees flexion, and the posterolateral bundle resists hyperextension and prevents posterior translation of the femur in extension 1, 2 .
What is the ACL?
Anterior cruciate ligament. The anterior cruciate ligament (ACL) is one of the two cruciate ligaments that stabilize the knee joint .
Is the ACL intracapsular or extracapsular?
Like the posterior cruciate ligament, the ACL is intracapsular but extrasynovial. The ACL consists of two components 4: anteromedial bundle (AMB) attaches to roof of intercondylar notch. posterolateral bundle (PLB) more vertically oriented, and slightly shorter. attaches to wall of intercondylar notch.
Is the anterior cruciate ligament heterogeneous?
Unlike other ligaments or tendons, the anterior cruciate ligament normally has a heterogeneous appearance and the anteromedial and posterolateral bundles are defined by surrounding high-intensity structures 1 .
Where is the ACL inserted?
The surgeon inserts the new ACL into the femur and tibia using a flexible guide wire.
What is ACL surgery?
ACL surgery is a repair or reconstruction of the anterior cruciate ligament (ACL). The ACL is an important soft-tissue structure in the knee that connects the femur to the tibia. A partially or completely torn ACL is a common injury among athletes. Complete ACL tears are usually treated by sports medicine physicians and orthopedic surgeons with an ACL reconstruction surgery, in which the torn ligament is replaced with a tissue graft to mimic the natural ACL. However, HSS takes an interdisciplinary approach to treating ACL injuries: Physiatrists, sports medicine physicians and orthopedic surgeons – along with radiology and rehabilitation professionals – collaborate to determine the best treatment option for each patient. Because people who have had an ACL injury are more likely to develop osteoarthritis in the knee earlier in life than those who do not, HSS physicians and scientists also continually investigate ACL surgery techniques to improve the short-term and long-term outcomes for patients.
What is the recovery time for ACL surgery?
It usually takes six to nine months for a patient to return to participating in sports after an ACL reconstruction, depending on the level of competition and the type of activity.
How soon should you get ACL surgery?
For a complete tear of the ACL, reconstruction surgery is generally scheduled for between three and six weeks after the injury occurs. This allows inflammation in the area to subside. If surgery is performed too early, patients may develop a profound scarring response called arthrofibrosis.
What kind of anesthesia is used for ACL surgery?
At HSS, most patients who undergo ACL reconstruction are given an epidural nerve block during their surgery, rather than being placed fully unconscious under general anesthesia. This epidural is the same type of regional anesthesia many women receive during childbirth.
Why do people have ACL surgery?
Because people who have had an ACL injury are more likely to develop osteoarthritis in the knee earlier in life than those who do not, HSS physicians and scientists also continually investigate ACL surgery techniques to improve the short-term and long-term outcomes for patients.
What is ACL repair?
ACL repair is an older technique that involved sewing the torn ACL tissue back together with sutures, rather than rebuilding it with a graft. ACL repair was performed in the 1970s at select institutions, including Hospital for Special Surgery, but was abandoned due to unacceptably high failure rates of up to 50%. Today, ACL repair has been modernized and can be performed through a minimally invasive approach. Some surgeons feel that modern ACL repair techniques may be performed safely and may lead to a quicker recovery than ACL reconstruction. However, the data on outcomes is limited, and failure rates for ACL repair appear to be between 5 and 10 times higher than those for ACL reconstruction in people of all ages.
What is the proximal end of the femur?
The proximal end of the femur (the part closest to the heart) is the head of the femur. The head of the femur is a ball that makes up part of the hip joint. It allows the leg to move at all angles. Below the head of the femur is the neck and the greater trochanter.
Where is the femur located?
The femur is found in the thigh. It is the largest bone in the body and is the only bone in the upper leg. The femur is known as a long bone. (There are four types of bone: long bones, short bones, flat bones, and irregular bones.) Long bones are longer than they are wide, with spongy bones at both ends and a cavity filled with bone marrow in ...
How long does it take to heal a femur fracture?
Femur fractures generally require surgical repair followed by several weeks of rehabilitation and physical therapy. Dislocations of the hip could require surgery depending on how severe the dislocation is. Physical therapy is almost always required.
How to tell if a hip fracture is a dislocation?
Hip dislocation occurs when the head of the femur is pulled away from the acetabulum (the socket in which the head of the femur rests). It is very difficult to identify the difference between a hip fracture (a broken head or neck of the femur) and a hip dislocation. Some healthcare providers ascribe fractures or dislocations depending on whether the patient's leg is rotated inwardly or outwardly after an injury. In reality, there is no way to tell the difference between a hip fracture or a hip dislocation other than with an X-ray.
What is the lower trochanter?
Below the lesser trochanter is the gluteal tuberosity, which is where the gluteus maximus is attached. The main shaft of the femur is known as the body of the femur.
Why is it so hard to fracture a femur?
It's usually very difficult since the femur is such a strong bone. Fractures are usually caused by a high-impact injury, such as falling from a height or a car accident. A fracture caused by a low-impact hit may indicate weaker bones due to a medical condition, such as osteoporosis. 2
How long is a femur?
The femur of an adult male is about 19 inches long and a bit under an inch in diameter. The proximal end of the femur (the part closest to the heart) is the head of the femur.
Introduction
Attachments
- Origin
Arises from the posteromedial corner of medial aspect of lateral femoral condyle in the intercondylar notch. This femoral attachment of ACL is on posterior part of medial surface of lateral condyle well posterior to longitudinal axis of the femoral shaft. The attachment is actuall… - Orientation
It runs inferiorly, medially and anteriorly.
Nerve Supply
- The ACL receives nerve fibers from the posterior articular branches of the tibial nerve. These fibers penetrate the posterior joint capsule and run along with the synovial and periligamentous vessels surrounding the ligament to reach as far anterior to the infrapatellar fat pad. Most of the fibers are associated with the endoligamentous vasculature and have a vasomotor function. Th…
Vascular Supply
- The major blood supply of the cruciate ligaments arises from the middle geniculate artery. The distal part of both cruciate ligaments is vascularized by branches of the lateral and medial inferior geniculate artery. The ligament is surrounded by a synovial fold where the terminal branches of the middle and inferior arteries form a periligamentous network. From the synovial sheath bloo…
Composition
- The ACL has a microstructure of collagen bundles of multiple types (mostly type I) and a matrix made of a network of proteins, glycoproteins, elastic systems, and glycosaminoglycans with multiple functional interactions.
Bundles
- There are two components of the ACL, the smaller anteromedial bundle (AMB) and the larger posterolateral bundle (PLB), named according to where the bundles insert into the tibial plateau. The anteromedial bundle is tight in flexion and the posterolateral bundle is tight in extension. In extension both bundles are parallel; in flexion the femoral insertion site of the posterolateral bun…
Function
- The ACL provides approximately 85% of total restraining force of anterior translation. It also prevents excessive tibial medial and lateral rotation, as well as varus and valgus stresses. To a lesser degree, the ACL checks extension and hyperextension. Together with the posterior cruciate ligament (PCL), the ACL guides the instantaneous center of rotation of the knee, therefore contr…
Introduction
Development of The ACL
- The knee originates from vascular femoral and tibial mesenchyme in the fourth week of gestation between the blastoma of femur and tibia. By 9 weeks, the Cruciate ligaments are composed of numerous immature fibroblasts having scanty cytoplasm and fusiform nuclei. After week 20, the remaining development consists of marked growth with little change in form. At these stages, t…
Gross Anatomy
- Femoral Attachment
The ACL is a band-like structure of dense connective tissues. The ACL is attached to a fossa on the posterior aspect of the medial surface of the lateral femoral condyle. The femoral attachment is in the form of a segment of a circle, with its anterior border straight and its posterior border co… - Tibial Attachment
The ACL is attached to a fossa in front of and lateral to the anterior tibial spine. At this attachment, the ACL passes beneath the transverse meniscal ligament, and a few fascicles of the ACL may blend with the anterior attachment of the lateral meniscus. In some instances, fascicle…
Micro Anatomy
- The complex ultra-structural organisation, the varied orientation of the bundles in the ACL, and the abundant elastic system make it very different from other ligaments and tendons. The ACL is a unique and complex structure able to withstand multiaxial stresses and varying tensile strains. Microscopically, we can distinguish three zones within the ACL: 1. The proximal part, which is le…
Biomechanics
- The fibre bundles of the ACL do not function as a simple band of fibres with constant tension; in fact, they show a different tensioning pattern throughout a full range of motion. The differentiation of the ACL into two functional bundles, the anteromedial bundle (AMB) and posterolateral bundle (PLB), seems an oversimplification, but the two bundle description of the fibres of the ACL has …
Structural and Mechanical Properties
- Structural properties can be described as the properties of the ligament or tendon together with its insertion site and fixation devices while mechanical properties can be defined as the properties of the ligament or replacement graft itself without its insertion sites. When a femur– ACL–tibia complex (FATC) is subjected to tensile testing, the resulting load-elongation curve represents th…
Effects of Muscle Stabilisation
- The muscles that cross the knee play a large role in maintaining the normal kinematics of the intact knee. Muscle activity can introduce large changes in the strains and forces experienced by the ACL. Markolf et al. found that passive extension of the knee generated forces in the ACL only during the last 100° of extension, whereas a 200N quadriceps tendon forces in the ACL caused f…
Overview
The anterior cruciate ligament (ACL) is one of a pair of cruciate ligaments (the other being the posterior cruciate ligament) in the human knee. The two ligaments are also called "cruciform" ligaments, as they are arranged in a crossed formation. In the quadruped stifle joint (analogous to the knee), based on its anatomical position, it is also referred to as the cranial cruciate ligament. The term cruciate translates to cross. This name is fitting because the ACL crosses the posterio…
Structure
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. The two bundles of the ACL are the anteromedial and the posterolateral, named according to where the bundles insert into the tibial plateau. The tibial plateau is a critical weight-bearing region on the upper extremity of the tibia. The ACL attaches in front of the intercondyloid eminence of the tibia, where it blends with the anterior hor…
Purpose
The purpose of the ACL is to resist the motions of anterior tibial translation and internal tibial rotation; this is important to have rotational stability. This function prevents anterior tibial subluxation of the lateral and medial tibiofemoral joints, which is important for the pivot-shift phenomenon. The ACL has mechanoreceptors that detect changes in direction of movement, position of the knee joint, and changes in acceleration, speed, and tension. A key factor in instab…
Clinical significance
An ACL tear is one of the most common knee injuries, with over 100,000 tears occurring annually in the US. Most ACL tears are a result of a non-contact mechanism such as a sudden change in a direction causing the knee to rotate inward. As the knee rotates inward, additional strain is placed on the ACL, since the femur and tibia, which are the two bones that articulate together forming the knee joint, move in opposite directions, causing the ACL to tear. Most athletes require reconstru…
Gallery
• 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
See also
• Posterior cruciate ligament
• Anterior cruciate ligament reconstruction
• Anterior drawer test
• Anterolateral ligament
External links
• Anatomy photo:17:02-0701 at the SUNY Downstate Medical Center - "Extremity: Knee joint"
• Anatomy figure: 17:07-08 at Human Anatomy Online, SUNY Downstate Medical Center - "Superior view of the tibia."
• Anatomy figure: 17:08-03 at Human Anatomy Online, SUNY Downstate Medical Center - "Medial and lateral views of the knee joint and cruciate ligaments."