Corpus: Ligament

A ligament is a coarse, fibrous connective tissue strand with a certain degree of elasticity that spans between two body parts and holds them in place.

In a narrower sense, the term is mainly used for the fibrous connections between skeletal elements, i.e., bones. However, in a broader sense, ligaments also serve to attach internal organs.

Ligaments are not distinct anatomical structures, but local fiber accumulations that continue with a smooth transition into the surrounding connective tissue. When they are part of a joint capsule, they are often difficult to differentiate during dissection.

The anatomical nomenclature of ligaments is not strictly systematic. Ligaments are usually named according to their course (e.g., calcaneocuboid ligament, interspinous ligament), but also according to their shape (e.g., bifurcate ligament, annular ligament of the radius), and rarely even based on their color (e.g., yellow ligament).

Ligaments running laterally to a joint are designated with the suffix "collateral," e.g., the fibular collateral ligament or the ulnar collateral ligament.

In the clinical context, abbreviations have been established, that can be derived from the German, Latin, or English terms. For example, the anterior cruciate ligament is referred to as "ACL" ("anterior cruciate ligament"), "VKB" ("vorderes Kreuzband"), or "LCA" ("ligamentum cruciatum anterius").

Like fascia and tendons, ligaments consist predominantly of dense, parallel-fibered connective tissue, that contains numerous type I collagen fibers. The cellular component of this bradytrophic form of connective tissue is low. Only a few cytoplasm-poor fibrocytes are arranged between the bundles of collagen fibers. In cross-sections, they are hardly visible under the microscope, or only as small triangles with long extensions ("wing cells").

Ligament attachments can be indirectly anchored to the bone via the periosteum, or extend into the bone directly with fiber bundles.

A smaller part of the ligaments, the so-called elastic ligaments, consists of dense, elastic connective tissue with a high proportion of elastic fibers. Examples include e.g.:

• Yellow ligament
• Nuchal ligament
• Suspensory ligament of the penis

Ligaments connect movable parts of the human skeleton with each other. In the area of the joints, they limit mobility to the physiologically desired extent, thus ensuring functional stability and guidance of the joint. In addition, together with the tendons and muscles they serve for the transmission of force during movements.

Their elasticity simultaneously provides a certain amount of leeway in joint guidance. This is necessary to adapt the musculoskeletal system flexibly to changing external influences, e.g., uneven terrain.

Important ligaments of the human body include, among others:

• Patellar ligament, a ligament connecting the kneecap (patella) to the tibia
• Anterior and posterior cruciate ligaments, the front and rear cruciate ligaments in the knee joint
• Falciform ligament, a sickle-shaped ligament in the abdominal cavity

Excessive strain on a ligament as a result of trauma can lead to ligament sprains or ruptures. Due to its histological properties, ligament tissue is only capable of limited regeneration, i.e. it heals with scarring. The newly formed connective tissue does not have the same biomechanical properties as the original tissue.

If a ligament rupture is not treated adequately, it can lead to instability of the involved joint, which poses a risk factor for later arthritis.

Ligaments can be used to replace other body structures as port of a ligamentoplasty.