Cruciate ligament

Type of ligament shaped like an X

Cruciate ligaments (also cruciform ligaments) are pairs of ligaments arranged like a letter X. They occur in several joints of the body, such as the knee joint, wrist joint
and the atlanto axial joint. 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.

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. They are named for their insertion into the tibia: the ACL attaches to the anterior aspect of the intercondylar area, the PCL to the posterior aspect. 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. 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. 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.

In the first edition of the official Latin nomenclature (Nomina Anatomica, renamed in 1998 as Terminologia Anatomica), the Latin expression ligamenta cruciata was used, similar to the expression cruciate ligaments currently in use in English. In classical Latin the verb cruciare is derived from crux, meaning cross. It became considered that cruciate was equivalent to cross shaped.