Tendons and Ligaments are the normal connective tissues present in our body having a property of visco-elasticity with great tensile strength and thus can regain their original structure or regular shape after any kind of deformation.1 These are actually composed of collagen fibres, fibroblast, and ground substances which make the building blocks of tendons and ligaments. These connective tissues are actually well managed to repair themselves after an injury by growing new fibres and other ground substances to retain their regular shape. Tendons and ligaments are actually dense regular connective tissue structures which are primarily arranged as parallel fibres. The cellular portion of these connective tissues is known as fibroblast and there is also the presence of extracellular matrix in tendons and ligaments similar to other connective tissues.
This current explanatory note on tendons and ligaments will make you aware of some of the major differences between tendon and ligament.
General Facts On The Basic Structure And Composition Of Tendons And Ligaments:
- Tendons and ligaments as explained above are the connective tissues composed of collagen fibres, fibroblast and the ground substances which are their building blocks.
- The extracellular matrix is filled with the ground substances and the collagen fibres; and the cellular portion known as fibroblast synthesizes and maintains the collagen fibres and the ground substances present in the extracellular matrix.
- The ground substance is made of glycosaminoglycans and proteoglycans which are linked to the collage fibres to form the connective tissue. This is actually the non fibrous portion of the tissues. This helps in tissue metabolism and provides support and shock absorption to the connective tissues.
- The fibrous portion of tendons and ligaments are composed of collagen fibres and some elastin.2 Fibrous part of tendons and ligaments is the supportive framework and makes up to 80% of the total weight in the connective tissues.
- The collagen fibres have a parallel arrangement in the tendons and ligaments. These fibers in their parallel arrangement state look wavy when in relaxed state while they are straight when under load or tension pull.
- Tendons and ligaments are surrounded by a sheath which helps while gliding on the contiguous structures. This sheath is made of loose connective areolar tissues.
Basic Difference Between Tendon And Ligament:
A tendon is a fibrous connective tissue which binds the muscles to bone; though a tendon can also attach the muscles to a structure like the eyeball. Generally tendons serve in the movement of bone or structure.
Ligament is also a fibrous connective tissues present in the body, however it binds the bone to bone and aids in keeping the bones stables and in their intact form or shape.
Difference Based On Structure Of Tendons And Ligaments:
When we look at the differences between tendon and ligament based on their structure; we can come up with the following description.
Tendons are long cylindrical structures with tightly packed collagen fibres which run longitudinal all the length and also comprises the cytoplasm with fibrocytes and the nuclei in it. Thus, tendon shows an orientation in the long axis direction. Apart from this, tendons are low at their healing process because they are relatively avascular as compared to the ligaments.
In case of ligaments the collagen fibres have comparatively smaller diameter than the tendons. Ligaments have primarily two kinds of orientations known as the parallel and the branching & interwoven orientation.
Difference Based On Composition Of Tendons And Ligaments:
Though the general composition of tendon and ligament remains the same, the percentages of the substances present in them do vary.
In case of tendons the collagen fibres are in higher percentage than in case of the ligaments. However the ligament comprises more of ground substances than the tendons. Tendons are more organized than the ligaments.
Difference Based On Function Of Tendons And Ligaments:
Now coming straight down to the differences based on the function, here we can present the description below.
Tendons have the following functions in our body.
- Transmit load or stress from muscle to bone or muscle to other structure like eyeball
- It has a great energy storing capacity
- Withstands more of tensile stresses as compared to the ligaments
- Tendons allow the muscle mass to remain at a convenient distance from the joints.
In case of ligaments, the functions can be explained in the following ways.
- Ligaments actually transmit load from bone to bone.
- They restrict the movement when compared to the tendons.
- Ligaments provide stability at the joints
- They hold the skeleton together and thus the bones are stable and in their shape standing intact.
Differences Based On Their Responses To Tensile Forces:
It is known that the tendon exhibits the highest tensile strength among any of the soft connective tissues. The tensile strength in case of tendon is noted to be 50-150 MPa. However it is comparatively low in case of ligament and may vary. So, responses tendon show to the tensile forces are comparatively fair than the responses shown in the ligaments
Injuries And Recovery Period Of Tendons And Ligaments:
Injuries to tendons and ligaments come either on a sudden trauma or the traumatic injury or may be on gradual and subsequent load or stress due to overuse of the fibrous connective tissues. An injury of tendon is termed as Tendonitis while the injury to ligament is usually termed as ligament sprain. In this current section we will discuss on the special kinds of injuries which affect the tendon and the injuries which affect the ligaments and also discuss on their healing process.
Before proceedings further on this, let us note that the injuries are usually classified into three prime categories or three grades namely grade 1, grade 2 and grade 3. In case of the grade 1 injury, the affected ligament or the tendon regains its resting length after the trauma and only some fibres meet with micro-failure. In case of the grade 2 injury, the degree of fibre rupture is pretty high and also the tendon/ligament doesn’t regain its resting length completely. In case of grade 3 injury, there is a serious gross disruption of the fibre and also instability or loss of function.
Injuries in tendon mostly come from overuse. About 50-60% of the sports personalities suffer from the overuse injury of tendons. Tendinitis is caused due to overuse of tendons. All kinds of degenerative tendon changes are caused due to overuse. Here occurs a repetitive micro-trauma in the tendons which overwhelms the ability of the connective tissue to adapt. Apart from this, there are also injuries occurring with substantial rupture in tendons. There occurs a serious traumatic injury in tendon when there is a tear in the tendon when there is a sudden stretching to a previously contracted muscle. Among other injuries to tendon there comes thermal injury, injuries due to dislocation etc.
Recovery and the Healing Process of Tendon Injuries:
Tendon healing generally includes the new tissue regeneration which are structurally and functionally similar to the normal tissues and also involve the scar repair.
The healing process in tendon can be explained under three phases, the inflammation, the proliferation or repair phase and the remodelling phase. In case of the inflammation phase the inflammatory cells like neutrophils and erythrocytes are inserted to the site of injury. Within a time of 24 hours macrophages and monocytes are recruited to the injury site. Then occurs the phagocytosis of the necrotic tissue in the injured site. Angiogenesis and proliferation of the tenocytes begins with the release of chemotactic and vasoactive factors. These tenocytes then move to the injury site and begins the repair of tissue in few days. After about six weeks of injury the remodelling begins.
Injuries in ligament are also common with athletes and as a matter of fact it occurs primarily with the athletic activities. Knee injuries like ACL( complete or partial tear of ligament due to sudden change of directions, landing from a jump in a wrong manner, direct ground contact etc; injuries like PCL occurring due to sprain in ligament because of overstretching and impacting the front knee; injuries like MCL.
It is known that ligament sprain begins from a minor single-fibre tear in the ligament due to over stretching. This gradually leads to swelling of the fibre and the fibres touch the ligament sheath or rub against the same. This further results in swelling in the sheath which gradually increases and results in a greater form of ligament tear leading to serious injuries.
Recovery and the Healing Process of Ligament Injuries:
Physiotherapy including the stretching exercises, series of motion tests etc, RICE or rest, ice treatment, compression and elevation, use of braces and crutches for support and in extreme cases surgery; are some of the most known ways of healing in ligament injury.