Hello! It’s been a while from the latest post on this series so I thought I’d continue the anatomy series and address ligament structures this time. I’ve previously written about bone (HERE), tendon (HERE) and muscle (HERE). In this post I’ll dive into the subject of ligament. As for the previous parts of this series I’ll tell a bit about general anatomy of ligaments but consider also the functional anatomy of ligaments as I presume most people would be more interested in the functional anatomy.
General anatomy. So what are ligaments? Ligaments are connective tissue structures that bind bones to each other. Ligaments consist from as you probably guessed water (65-75 % it’s funny how almost all of the structures in the body contain about this much water as human being in general consists from water about 75 %. If we go even further from this the earth is about 70 % covered with water. For me this is kind of fascinating. 🙂 Same thing with other substances and trace elements in the body. But yeah back to the subject!) Ligaments also have ligamentocytes that are the ligament cells. Other substances in ligament tissue are collagen (mostly type I and small amount of type III), proteoglycans and elastin. Compared with tendons in ligaments there is more elastin which favors tendons in regards of tensile strength.
There are many shapes and sizes of ligaments. Ligament structure varies depending on the site where it is located and also what kind of function it has. For example the anterior cruciate ligament in the knee is strong, thick and spiraled because it has to limit the forward movement of the rather large shin bone. Then there are ligaments like the deltoid ligament that is large fan-shaped structure extending on the inner surface of the ankle. Ligaments can also be band like structures from one bone to other like glenohumeral ligaments in the shoulder.
Functional anatomy. Ligaments are strong structures that support joints. The tensile strength of ligaments is based on the collagen filaments that are organized in a way that restricts tensile forces. This is important during any kind of movement in the body. Ligaments are important supporting structures and belong to one of the three groups that Panjabi described in his joint stability theory. Ligaments belong together with bones and discs to the passive support subsystem that ensures the joint integrity. This is important to remember as if for example the active subsystem doesn’t work properly more proportion of support goes to the passive subsystem. Have you had pain in the back just when you go to bed after a long day and lie on your back that resolves in a few minutes lying still? That’s your ligaments. Most likely the active subsystem (muscles) has gotten tired during the day and your joints have hung on the support of ligaments.
Support system. Ligaments are important in the proprioception of the body. Proprioception means the ability to sense the position and movements of the body and different body parts. There are receptors in the joints that sense that position of that particular joint. These receptors send impulses to the central nervous system that interprets these impulses and modifies for example muscle activation according to this information. It has to be known that anyway there are these receptors in ligaments they react mostly when the joint is in the end range of motion so they aren’t that sensitive to milder movements.
Training affects ligaments. Training improves the tensile strength of the ligaments as they have to get stronger to cope with bigger forces. This is achieved via changes in the ligament’s collagen organization. The collagen filaments organize in a more structured way after training stimulus and the tensile strength of the ligament improves.
Injuries. Ligaments are quite often injured especially in sports participation. Common injuries are sprains and strains. These usually resolve with conservative treatment which means rest for certain period depending the injury site and active rehabilitation with different corrective exercises. Sometimes the ligaments are ruptured. Even then conservative treatment is tried sometimes but mostly in total ligament ruptures the treatment would be operative re-attachment of the ligament.
So hope this article was informative and clarified the topic of ligament. If any questions or thoughts come to your mind, feel free to share them in the comments. Soon I’ll have the full series of the musculoskeletal system. There are few more topics to discuss but until then I want to say thank you for reading the article and hope you enjoyed this!
Have a nice day!
Peace and Love!