Ligament

Ligament
Diagram of the right knee.
Typical joint

In anatomy, the term ligament is used to denote any of three types of structures.^[1] Most commonly, it refers to fibrous tissue that connects bones to other bones and is also known as articular ligament, articular larua,^[2] fibrous ligament, or true ligament.

Ligament can also refer to:

• Peritoneal ligament: a fold of peritoneum or other membranes.
• Fetal remnant ligament: the remnants of a tubular structure from the fetal period of life.

The study of ligaments is known as desmology (from Greek δεσμός, desmos, "string"; and -λογία, -logia).

Articular ligaments

"Ligament" most commonly refers to a band of tough, fibrous dense regular connective tissue comprising attenuated collagenous fibers. Ligaments connect bones to other bones to form a joint. They do not connect muscles to bones; that is the job of tendons. Some ligaments limit the mobility of articulations, or prevent certain movements altogether.

Capsular ligaments are part of the articular capsule that surrounds synovial joints. They act as mechanical reinforcements. Extra-capsular ligaments join together and provide joint stability. Intra-capsular ligaments, which are much less common,^{[citation needed]} also provide stability but permit a far larger range of motion. Cruciate ligaments occur in pairs.

Ligaments are viscoelastic. They gradually lengthen when under tension, and return to their original shape when the tension is removed. However, they cannot retain their original shape when stretched past a certain point or for a prolonged period of time. This is one reason why dislocated joints must be set as quickly as possible: if the ligaments lengthen too much, then the joint will be weakened, becoming prone to future dislocations.^{[citation needed]} Athletes, gymnasts, dancers, and martial artists perform stretching exercises to lengthen their ligaments, making their joints more supple.

The term "double-jointed" refers to people with more-elastic ligaments, allowing their joints to stretch and contort further. The medical term for describing such double-jointed persons is hyperlaxity.

The consequence of a broken ligament can be instability of the joint. Not all broken ligaments need surgery, but, if surgery is needed to stabilise the joint, the broken ligament can be repaired. Scar tissue may prevent this. If it is not possible to fix the broken ligament, other procedures such as the Brunelli procedure can correct the instability. Instability of a joint can over time lead to wear of the cartilage and eventually to osteoarthritis.

Examples

Head and neck Cricothyroid ligament Periodontal ligament Suspensory ligament of the lens Thorax Suspensory ligament of the breast Pelvis Anterior sacroiliac ligament Posterior sacroiliac ligament Sacrotuberous ligament Sacrospinous ligament Inferior pubic ligament Superior pubic ligament Suspensory ligament of the penis

Wrist Palmar radiocarpal ligament Dorsal radiocarpal ligament Ulnar collateral ligament Radial collateral ligament Knee Anterior cruciate ligament (ACL) Lateral collateral ligament (LCL) Posterior cruciate ligament (PCL) Medial collateral ligament (MCL) Cranial cruciate ligament (CrCL) - quadruped equivalent of ACL Caudal cruciate ligament (CaCL) - quadruped equivalent of PCL Patellar ligament

Peritoneal ligaments

Certain folds of peritoneum are referred to as ligaments. Examples include:

• The hepatoduodenal ligament, that surrounds the hepatic portal vein and other vessels as they travel from the duodenum to the liver.
• The broad ligament of the uterus, also a fold of peritoneum.

Fetal remnant ligaments

Certain tubular structures from the fetal period are referred to as ligaments after they close up and turn into cord-like structures:^{[citation needed]}

Fetal	Adult
ductus arteriosus	ligamentum arteriosum
extra-hepatic portion of the fetal left umbilical vein	ligamentum teres hepatis (the "round ligament of the liver").
intra-hepatic portion of the fetal left umbilical vein (the ductus venosus)	ligamentum venosum
distal portions of the fetal left and right umbilical arteries	medial umbilical ligaments

See also

• Broström procedure

References

1. ^ ligament at eMedicine Dictionary
2. ^ "ligament" at Dorland's Medical Dictionary