Tendons are anatomical structures, composed mainly of connective tissue (a group of cells that have the same function). These serve to unite the muscles with the bones; as well as, to function by sending the energy emanated by the muscles towards the bones and that allow the movement of the different parts of the body. It should be noted that together with the ligaments, the tendons are responsible for supporting the muscles of the body.

What is the function of tendons?

Tendons are a kind of cords, made up of connective tissue and other proteins (collagen and elastin), which connect muscles and bones, which makes their movements possible (extension and flexion). The fibrous structure of the tendons, allows them to develop various functions in the body; the main one is the union or connection of the bones and muscles. In turn, the collagen and elastin contained in these, provide it with other qualities, among which the following can be mentioned:

Power connection and transmission

The main function of the tendons is to connect the muscles with the bones, to generate the necessary movement. For this, the tendons act as a bridge between the muscles and the bony segments (bones), through which the force that produces the movement of the parts of the body is sent.

In turn, tendons have the ability to store, transmit and recover the energy required in each movement of the body; In this sense, it is in them where the muscular force that allows the bones and joints to be moved is administered.


During physical activity, the muscles of the body (especially the legs) store and expel energy, capable of mobilizing the different parts of the body. In this sense, the tendons perform a cushioning function to prevent injury to the muscles. In this way, when the fascicles of the muscles get rid of the energy that enhances movement, the tendons act by absorbing this energy to prevent it from causing serious injury to the muscles.

Positioning and stability

The tendons, in addition to connecting the muscles with the bones, transferring and absorbing energy, also serve to give stability to the bones during a specific activity or movement. An example of this, it is time to write by hand, during this movement, the tendons serve as support to maintain a consistent posture; as well as providing stability to the bones and muscles it connects.

Tendon composition

The correct functioning of the tendons is due to their composition, which is as follows:


Collagen is a collagen fiber-forming protein, its main function is to provide resistance and strength during stretching, which is why it is present in large percentages in tendons.


Like collagen, elastin is a protein found in tendons and other anatomical structures, such as the skin. This, in addition to collaborating in the contribution of strength and resistance, also provides the tendons with elasticity and stability.

extracellular matrix

It is a network composed of collagen, base substance and glycoproteins. Likewise, in the extracellular or intercellular matrix of tendons, are the cellular structures, tenocytes and tenoblasts.

Base substance

Also known as a fundamental substance, it is in charge of ordering the collagen fibers and connective tissue, which determine the final shape of the tendons. They consist mainly of water and mucopolysaccharides.

Tenocytes and tenoblasts

90% of the cellular components of tendons are tenocytes and tenoblasts, the former are responsible for the manufacture of extracellular elements of the tendon matrix.

For their part, tenoblasts are cellular structures whose function is to synthesize the proteins of the tendon matrix; as well as organizing and transforming collagen networks in tendon tissue recovery processes.

Types of tendons

Tendons can be classified into two large groups, according to the function they fulfill in the different parts of the body. In this way, there are two types of tendons with different qualities, the extensor tendons and the flexor tendons.

Extensor tendons

The extensor tendons are those that allow the extension, strain or enlargement of a part of the body. It is an example of extensor tendons, those found in the fingers of the hands and are capable of stretching this part of the human body.

Flexor tendons

The flexor tendons fulfill a function contrary to the extensor tendons, these are in charge of contracting or flexing a part of the body. In this sense, if the extensor tendons allow the fingers of the hand to be stretched, the flexor tendons perform the opposite movement, flexing the fingers, when they receive a signal from the brain.

Tendon Injuries: Which are the Most Common?

Tendons are structures that are constantly subjected to great efforts, whether you play a sport or not, although it must be emphasized that if you practice a sport, there are more chances of suffering tendon injuries. This continuous and recurrent use of tendons makes them susceptible to mild to severe injuries, which can also be caused by other inflammatory diseases and the skeletal system.

Among the injuries that can be suffered in the tendons, are the following:


It is known as tendinitis to the inflammation of the tendons, it is characterized by swelling around the joints, pain and limitation of movement. The main cause of tendinitis is the frequent repetition of a movement, which is why it is common in athletes and sportsmen.

On the other hand, the treatment for tendonitis consists mainly of analgesics to reduce pain and corticosteroids that minimize inflammation. However, depending on the severity of the injury, physical therapy or surgery may be necessary.


Tenosynovitis includes, in addition to inflammation of the tendons (tendonitis), inflammation of the sheath that covers and protects them. This type of injury can be caused by other inflammatory diseases such as rheumatoid arthritis.

To treat this injury, analgesic and anti-inflammatory medications are used, likewise, splints can be used to immobilize the affected areas and avoid pain that occurs with movement.


For its part, tendinosis is a chronic injury to the tendons, characterized not only by their inflammation, but also includes the degeneration or wear of the tissues that make up the tendons.

In general, tendinosis appears after an untreated tendonitis or whose treatment was not totally effective, which is why the symptoms are similar to this one. However, the treatment of tendinosis is not based on anti-inflammatory drugs, since it must be treated with physiotherapeutic techniques.

Tendon rupture

A tendon tear is the rupture of the tendons, which causes the loss of continuity of the tissues that make up these anatomical structures. In this sense, the most common causes of this injury are muscle overexertion, calcium deficiency and poor position.

Regarding the treatment for tendon rupture, it is mainly based on the immobilization of the parts, with the aim of keeping the tissues as united or close as possible and that the union of the tissue is achieved in a natural way.

Tendons and ligaments of the human body

Tendons and ligaments are important structures of the human leather, which provide stability, flexibility and movement to other structures (bones, muscles and joints). In this sense, although tendons and ligaments share some characteristics, such as their composition, they have some anatomical differences presented below:

What are ligaments and what are their functions?

Ligaments are fibrous structures that connect the bones of the joints, which allows their movement and stabilization. Like tendons, they are composed of collagen and elastin, which provide strength and elasticity.

In terms of their functions, ligaments are responsible for the connection between two bones and allow them to move and support themselves. In other words, they provide stability to the various anatomical structures in which they are found.

It should be emphasized that the ligaments are also responsible for allowing or restricting joint movements; in this case, they allow natural movements and restrict those that can cause injuries.

Ligaments of the human body

Ligaments are found in different joints of the human body, among them are the following:

  • Spine.
  • Sacro-iliac joint.
  • Elbow and shoulder joint.
  • Knee joint.

Tendons of the human body

For its part, the human body also has a large number of tendons, spread over their entire length. The best known are the following:

  • Achilles tendon (calf).
  • Patellar tendon (knee).
  • Elbow tendons.
  • Tendons of hands and feet.

Conclusion: Are tendons essential for humans?

Tendons are tissues in the human body, which serve to connect and allow movement between muscles and bones. Their importance lies in the fact that they are responsible for the mobilization of different parts of the body, such as fingers, hands, feet and knees. That is why they are prone to injuries ranging from mild to serious and that can have consequences such as the loss of functionality of any part of the body.

Samantha Robson
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Dr. Samantha Robson ( CRN: 0510146-5) is a nutritionist and website content reviewer related to her area of ​​expertise. With a postgraduate degree in Nutrition from The University of Arizona, she is a specialist in Sports Nutrition from Oxford University and is also a member of the International Society of Sports Nutrition.

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