Ligament

Ligament
Diagram of the right knee.
Typical joint
Latin	ligamenta

In anatomy, the term ligament is used to denote three different types of structures:^[1]

1. Articular ligaments: Fibrous tissue that connects bones to other bones. They are sometimes called "articular larua"^[2], "fibrous ligaments", or "true ligaments".
2. Peritoneal ligaments: A fold of peritoneum or other membranes.
3. Fetal remnant ligaments: The remnants of a tubular structure from the fetal period of life.

The first term is the one most commonly intended when using the word "ligament". This article briefly handles peritoneal and fetal remnant ligaments before focusing on articular legments.

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

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:

Articular ligaments

In its most common use, a ligament is 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, also provide stability but permit a far larger range of motion. Cruciate ligaments occur in pairs.

Ligaments are elastic; they gradually lengthen when under tension, and return to their original shape when the tension is removed. This is in contrast with tendons, which are inelastic. However, ligaments can be plastic (i.e. retaining their changed 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. 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 who have more elastic ligaments, allowing their joints to stretch and contort further. The medical term for describing such double-jointed persons is hyperlaxity and double-jointed is a synonym of hyperlax.

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

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

Head and neck

• Cricothyroid ligament
• Periodontal ligament
• Suspensory ligament of the lens

Pelvis

• Anterior sacroiliac ligament
• Posterior sacroiliac ligament
• Sacrotuberous ligament
• Sacrospinous ligament
• Inferior pubic ligament
• Superior pubic ligament
• Suspensory ligament of the penis

Thorax

• Suspensory ligament of the breast

Wrist

• Palmar radiocarpal ligament
• Dorsal radiocarpal ligament
• Ulnar collateral ligament
• Radial collateral ligament

See also

• Joint
• Brostrom procedure

References

1. ↑ ligament at eMedicine Dictionary
2. ↑ ligament at Dorland's Medical Dictionary

External links

• Exhaustive list of ligaments

ligaments attach bone to bone