Ligament: Anterior cruciate ligament
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 (ACL) is a cruciate ligament which is one of the four major ligaments of the human knee. In the quadruped stifle (analogous to the knee), based on its anatomical position, it is referred to as the cranial cruciate ligament.^[1]

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 of the tibia, being blended with the anterior horn of the medial meniscus. These attachments allow it to resist anterior translation and medial rotation of the tibia, in relation to the femur.

Injury[link]

A 2010 Los Angeles Times review of two seemingly conflicting medical studies discussed whether ACL reconstruction was advisable. One study found that children under 14 who had ACL reconstruction fared better after early surgery than those who underwent a delayed surgery. For adults under 35, though, patients who underwent early surgery followed by rehab fared no better than those who had rehab therapy and a later surgery.^[2]

The first report focused on children and the timing of an ACL reconstruction. ACL injuries in children are a challenge because children have open growth plates in the bottom of the femur or thigh bone and on the top of the tibia or shin. An ACL reconstruction will typically cross the growth plates, posing a theoretical risk of injury to the growth plate, stunting leg growth or causing the leg to grow at an unusual angle. ^[3]

The second study noted in the L.A. Times piece focused on adults and questioned whether an ACL reconstruction was necessary when an MRI-is not merely an existing tear;^{[clarification needed]} many patients without instability, buckling or giving way after a course of rehabilitation can be managed non-operatively.^[2] Patients involved in sports requiring significant cutting, pivoting, twisting, or rapid acceleration or deceleration may not be able to participate in these activities without ACL reconstruction. The randomized control study was originally published in the New England Journal of Medicine.^[4]

Additional images[link]

• 

  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.

• 

  An anterior view of the right knee, showing anterior cruciate ligament with anteromedial (AM) and posterolateral (PL) bundles.

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  Anterior cruciate ligament (surrounded by synovium) during knee arthroscopy. Lateral epicondylus of the femur can be seen to the right.

• 

  Magnetic resonance imaging evaluation demonstrates normal signal of both anterior and posterior cruciate ligaments (arrows).

See also[link]

• Anterior cruciate ligament reconstruction
• Anterior drawer test
• Lateral collateral ligament
• Medial collateral ligament
• Posterior cruciate ligament
• Unhappy triad

References[link]

External links[link]

• 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."
• lljoints at The Anatomy Lesson by Wesley Norman (Georgetown University) (antkneejointopenflexed)

Illustration of the ligaments of the knee, including the anterior and posterior cruciate ligaments

Cruciate ligaments (also cruciform ligaments) are pairs of ligaments arranged like a letter X.^[1] They occur in several joints of the body, such as the knee. In a fashion similar to the cords in a toy Jacob's ladder, the crossed ligaments stabilize the joint while allowing a very large range of motion.

Etymology[link]

Look up cruciate or ligament in Wiktionary, the free dictionary.

The adjective cruciate is from the Latin crux, crucis, meaning "cross".

In Classical Latin, the verb cruciare means "to torture". By the time in the Late Latin period when Latin medical terminology was being established, this old meaning of cruciare seems to have fallen out of use in common speech, and the word was re-invented with the meaning "arrange in cross shape". Use of "cruciat-" to refer to torture is now obsolete in English, but this old usage is shown in the common English word excruciating, and in the "Cruciatus" curse in the Harry Potter fictional scenario.

Anatomy[link]

Cruciate ligaments occur in the knee of humans and other bipedal animals and the corresponding stifle of quadrupedal animals, and in the neck, fingers, and foot.

• The cruciate ligaments of the knee are the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL). These ligaments are two strong, rounded bands that extend from the head of the tibia to the intercondyloid notch of the femur. The ACL is lateral and the PCL is medial. They cross each other like the limbs of an X. The ACL and PCL remain distinct throughout and each has its own partial synovial sheath. Relative to the femur, the ACL keeps the tibia from slipping forward and the PCL keeps the tibia from slipping backward.
• Another structure of this type in human anatomy is the cruciate ligament of the dens of the atlas vertebra, also called "cruciform ligament of the atlas", a ligament in the neck forming part of the atlanto-axial joint.^[2]
• In the fingers, the deep and superficial flexor tendons pass through a fibro-osseous tunnel system – the flexor mechanism – of annular and cruciate ligaments called pulleys. The cruciate pulleys tether the long flexor tendons. The number and extent of these cruciate and annular ligaments varies among individuals, but three cruciate and four or five annular ligaments are normally found in each finger (usually referred to as, for example, "A1 pulley" and "C1 pulley"). The thumb has a similar system for its long flexor tendon but with a single oblique pulley replacing the cruciate pulleys found in the fingers.^[3]
• The human foot has a cruciate crural ligament, also known as inferior extensor retinaculum of foot. The equine foot has a pair of cruciate distal sesamoidean ligaments in the metacarpophalangeal joint. These ligaments can be seen using computed tomography.^[4]

Epidemiology of rupture[link]

Rupture of the cranial cruciate ligament is one of the "most frequent acquired diseases of the stifle joint"^[5] in humans, dogs, and cats; direct trauma to the joint is relatively uncommon and age appears to be a major factor.^[5]

Cruciate ligament injuries are common in animals, and in 2005 a study estimated that $1.32 billion was spent in the United States in treating the cranial cruciate ligament of dogs.^[6]

References[link]