Myotendinous Junction: Difference between revisions

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'''Original Editor '''- [[User:User Name|User Name]]
'''Original Editor '''- [[User:Lucinda hampton|Lucinda hampton]]


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'''Top Contributors''' - {{Special:Contributors/{{FULLPAGENAME}}}}  &nbsp;   
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== Introduction ==
== Introduction ==
[[File:Medial view of a cadaver dissection of the gastrocnemius–soleus junction.png|thumb|Dissection of the gastrocnemius–soleus MTJ]]
[[File:Myotendinous junction structure.png|thumb|459x459px|MTJ structure|alt=]]
Myotendinous junction (MTJ) is a part of the myotendinous unit, which connects muscle and tendon, and transmits forces between them.
Myotendinous junction (MTJ) is a part of the myotendinous unit. The myotendinous unit  consists usually of [[bone]], enthesis, [[Tendon Anatomy|tendon]], myotendinous junction and [[Muscle Cells (Myocyte)|muscle]], and is responsible for producing skeletal movement<ref>Radiopedia Myotendinous unit Available: https://radiopaedia.org/articles/myotendinous-unit?lang=us<nowiki/>(accessed 12.6.2022)</ref>.


The MTJ has a unique morphology with a highly folded muscle membrane filled with invaginations of collagen fibrils from the tendon. This creates an increased area of force transmission between muscle and tendon and, as a result, disperses the energy of a contracting muscle decreasing focal stress<ref name=":0">Radiopedia Myotendinous junction Available:https://radiopaedia.org/articles/myotendinous-junction?lang=us (accessed 12.6.2022)</ref><ref name=":1">Jakobsen JR, Krogsgaard MR. The Myotendinous Junction—A Vulnerable Companion in Sports. A Narrative Review. Frontiers in physiology. 2021;12. Available;https://www.frontiersin.org/articles/10.3389/fphys.2021.635561/full (accessed 12.6.2022)</ref>.
The MTJ has a distinctive form with the muscle membrane having many  infolds which  the [[collagen]] fibrils from the tendon join with (see image 1) . This unique structure creates an increased area for force transmission between muscle and tendon resulting in better force dispersal and less focal [[Stress Loading|stress]]<ref name=":0">Radiopedia Myotendinous junction Available:https://radiopaedia.org/articles/myotendinous-junction?lang=us (accessed 12.6.2022)</ref><ref name=":1">Jakobsen JR, Krogsgaard MR. The Myotendinous Junction—A Vulnerable Companion in Sports. A Narrative Review. Frontiers in physiology. 2021;12. Available;https://www.frontiersin.org/articles/10.3389/fphys.2021.635561/full (accessed 12.6.2022)</ref>.


During muscle activity and mainly during high effort exercise, large forces are transmitted from muscle fibers to the tendon through the MTJ. It is a common location for strain injuries in sports. Most of these can be prevented by heavy eccentric exercise<ref name=":1" />.
The MTJ transmits large forces from muscle to tendon in strenuous exercise, and hence is a common location for muscle strains. Most of these can be prevented by heavy eccentric exercise<ref name=":1" />.  


The surface area between muscle and tendon is enlarged by foldings of tendon into muscle, and this reduces stress between the tissues.  
== Physiotherapy Implications ==
[[File:Medial view of a cadaver dissection of the gastrocnemius–soleus junction.png|thumb|Dissection of the gastrocnemius–soleus MTJ|alt=|333x333px]]
The myotendinous unit weakest region is the MTJ, and as such it is its most commonly injured part.


* In animals, the size and number of foldings are increased as a response to heavy training and reduced during inactivity.  
* Large pennate muscle that are multi arthrodial  and produce large tensile stresses are the most likely to suffer from MTJ injuries e.g. [[Biceps Femoris|biceps femoris]], [[Quadratus Femoris|quadratus femoris]], [[Biceps Brachii|biceps brachii]]<ref name=":0" />.
* In humans, the muscle fibers near the MTJ show very high rates of remodeling compared to other regions of the muscle.
* The interdigitations of the MTJ become shorter with aging, lessening the contact area for force transmission, and increase risk of injury.<ref>Wikimsk MTJ Available:https://wikimsk.org/wiki/Myotendinous_Junction (accessed 12.6.2022)</ref>
 
== Physiotherapy Implications ==
[[File:Myotendinous junction structure.png|thumb|392x392px|MTJ structure]]
In a healthy adult, the MTJ is the weakest region of the myotendinous unit and for that reason it is its most commonly injured part.


The highest risk of strain occurs in large pennate muscles that cross two joints and produce large tensile forces e.g. biceps femoris, quadratus femoris, biceps brachii<ref name=":0" />.
== US and MRI ==
For correct diagnosis  a grading system of MTJ injuries exists based on [[MRI Scans|MRI]] or [[Ultrasound Scans|US]] scan results.


== Resources  ==
# Mild [[Muscle Strain|strain]]: feathery interstitial edema and fluid/hemorrhage around the MTJ
*bulleted list
# Moderate strain: intramuscular hematoma and perifascial fluid/hemorrhage
*x
# Severe strain: MTJ tear with laxity/discontinuity of the tendon and muscle ends, sometimes with retraction
or


#numbered list
[[Scar Management|Scar tissue]], old [[Blood Physiology|blood]] products and atrophy/fatty degeneration of the muscle are indicative of an old strain<ref name=":0" />.
#x
[[File:Myotendinous junction and enthesis combined.png|center|thumb|826x826px|Myotendinous unit]]


== References  ==
== References  ==


<references />
<references />
[[Category:Musculoskeletal/Orthopaedics]]
[[Category:Muscles]]
[[Category:Muscle strain]]
[[Category:Tendinopathy]]
[[Category:Sports Injuries]]

Latest revision as of 02:33, 14 June 2022

Original Editor - Lucinda hampton

Top Contributors - Lucinda hampton  

Introduction[edit | edit source]

MTJ structure

Myotendinous junction (MTJ) is a part of the myotendinous unit. The myotendinous unit consists usually of bone, enthesis, tendon, myotendinous junction and muscle, and is responsible for producing skeletal movement[1].

The MTJ has a distinctive form with the muscle membrane having many infolds which the collagen fibrils from the tendon join with (see image 1) . This unique structure creates an increased area for force transmission between muscle and tendon resulting in better force dispersal and less focal stress[2][3].

The MTJ transmits large forces from muscle to tendon in strenuous exercise, and hence is a common location for muscle strains. Most of these can be prevented by heavy eccentric exercise[3].

Physiotherapy Implications[edit | edit source]

Dissection of the gastrocnemius–soleus MTJ

The myotendinous unit weakest region is the MTJ, and as such it is its most commonly injured part.

  • Large pennate muscle that are multi arthrodial and produce large tensile stresses are the most likely to suffer from MTJ injuries e.g. biceps femoris, quadratus femoris, biceps brachii[2].
  • The interdigitations of the MTJ become shorter with aging, lessening the contact area for force transmission, and increase risk of injury.[4]

US and MRI[edit | edit source]

For correct diagnosis a grading system of MTJ injuries exists based on MRI or US scan results.

  1. Mild strain: feathery interstitial edema and fluid/hemorrhage around the MTJ
  2. Moderate strain: intramuscular hematoma and perifascial fluid/hemorrhage
  3. Severe strain: MTJ tear with laxity/discontinuity of the tendon and muscle ends, sometimes with retraction

Scar tissue, old blood products and atrophy/fatty degeneration of the muscle are indicative of an old strain[2].

Myotendinous unit

References[edit | edit source]

  1. ↑ Radiopedia Myotendinous unit Available: https://radiopaedia.org/articles/myotendinous-unit?lang=us(accessed 12.6.2022)
  2. ↑ 2.0 2.1 2.2 Radiopedia Myotendinous junction Available:https://radiopaedia.org/articles/myotendinous-junction?lang=us (accessed 12.6.2022)
  3. ↑ 3.0 3.1 Jakobsen JR, Krogsgaard MR. The Myotendinous Junction—A Vulnerable Companion in Sports. A Narrative Review. Frontiers in physiology. 2021;12. Available;https://www.frontiersin.org/articles/10.3389/fphys.2021.635561/full (accessed 12.6.2022)
  4. ↑ Wikimsk MTJ Available:https://wikimsk.org/wiki/Myotendinous_Junction (accessed 12.6.2022)
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