Cruciate ligament
Encyclopedia
Cruciate ligaments are pairs of ligaments arranged like a letter X
X
X is the twenty-fourth letter in the basic modern Latin alphabet.-Uses:In mathematics, x is commonly used as the name for an independent variable or unknown value. The usage of x to represent an independent or unknown variable can be traced back to the Arabic word šay شيء = “thing,” used in Arabic...

. They occur in several joint
Joint
A joint is the location at which two or more bones make contact. They are constructed to allow movement and provide mechanical support, and are classified structurally and functionally.-Classification:...

s of the body, such as the knee
Knee
The knee joint joins the thigh with the leg and consists of two articulations: one between the fibula and tibia, and one between the femur and patella. It is the largest joint in the human body and is very complicated. The knee is a mobile trocho-ginglymus , which permits flexion and extension as...

. In a fashion similar to the cords in a toy Jacob's ladder
Jacob's ladder (toy)
A Jacob's ladder is a folk toy consisting of blocks of wood held together by strings or ribbons. When the ladder is held at one end, blocks appear to cascade down the strings. However, this effect is a visual illusion which is the result of one block after another flipping over...

, the crossed ligaments stabilize the joint while allowing a very large range of motion.

Etymology

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

In Classical Latin
Classical Latin
Classical Latin in simplest terms is the socio-linguistic register of the Latin language regarded by the enfranchised and empowered populations of the late Roman republic and the Roman empire as good Latin. Most writers during this time made use of it...

, the verb cruciare means "to torture
Torture
Torture is the act of inflicting severe pain as a means of punishment, revenge, forcing information or a confession, or simply as an act of cruelty. Throughout history, torture has often been used as a method of political re-education, interrogation, punishment, and coercion...

". By the time in the Late Latin
Late Latin
Late Latin is the scholarly name for the written Latin of Late Antiquity. The English dictionary definition of Late Latin dates this period from the 3rd to the 6th centuries AD extending in Spain to the 7th. This somewhat ambiguously defined period fits between Classical Latin and Medieval Latin...

 period when Latin medical terminology
Medical terminology
Medical terminology is a vocabulary for accurately describing the human body and associated components, conditions, processes and process in a science-based manner. Some examples are: R.I.C.E., trapezius, and latissimus dorsi. It is to be used in the medical and nursing fields...

 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
Harry Potter
Harry Potter is a series of seven fantasy novels written by the British author J. K. Rowling. The books chronicle the adventures of the adolescent wizard Harry Potter and his best friends Ron Weasley and Hermione Granger, all of whom are students at Hogwarts School of Witchcraft and Wizardry...

 fictional scenario.

Anatomy

Cruciate ligaments occur in the knee
Knee
The knee joint joins the thigh with the leg and consists of two articulations: one between the fibula and tibia, and one between the femur and patella. It is the largest joint in the human body and is very complicated. The knee is a mobile trocho-ginglymus , which permits flexion and extension as...

 of humans and other bipedal animals and the corresponding stifle
Stifle joint
The 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...

 of quadrupedal animals, and in the neck
Neck
The neck is the part of the body, on many terrestrial or secondarily aquatic vertebrates, that distinguishes the head from the torso or trunk. The adjective signifying "of the neck" is cervical .-Boner anatomy: The cervical spine:The cervical portion of the human spine comprises seven boney...

, fingers, and foot.
  • The cruciate ligaments of the knee are the anterior cruciate ligament
    Anterior cruciate ligament
    The anterior cruciate ligament is a cruciate ligament which is one of the four major ligaments of the human knee. In the quadruped stifle , 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...

     (ACL) and the posterior cruciate ligament
    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...

     (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
    Atlanto-axial joint
    The Atlanto-axial joint is of a complicated nature. It consists of no fewer than four distinct joints....

    .
  • In the fingers, the deep
    Flexor digitorum profundus muscle
    - References :...

     and superficial flexor tendons
    Flexor digitorum superficialis muscle
    Flexor digitorum superficialis is an extrinsic flexor muscle of the fingers at the proximal interphalangeal joints....

     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
    Flexor pollicis longus muscle
    The flexor pollicis longus is a muscle in the forearm and hand that flexes the thumb...

     but with a single oblique pulley replacing the cruciate pulleys found in the fingers.
  • The human foot has a cruciate crural ligament
    Cruciate crural ligament
    The inferior extensor retinaculum of the foot is a Y-shaped band placed in front of the ankle-joint, the stem of the Y being attached laterally to the upper surface of the calcaneus, in front of the depression for the interosseous talocalcanean ligament; it is directed medialward as a double...

    , 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
    Computed tomography
    X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...

    .

Epidemiology of rupture

Rupture of the cranial cruciate ligament is one of the "most frequent acquired diseases of the stifle joint
Stifle joint
The 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...

" in humans, dogs, and cats; direct trauma to the joint is relatively uncommon and age appears to a major factor.

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.
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