Myotendinous Junction: Difference between revisions

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


'''Top Contributors''' - {{Special:Contributors/{{FULLPAGENAME}}}}  &nbsp;   
'''Top Contributors''' - {{Special:Contributors/{{FULLPAGENAME}}}}  &nbsp;   
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== Introduction ==
== Introduction ==
[[File:Myotendinous junction structure.png|thumb|392x392px|MTJ structure]]
[[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:Medial view of a cadaver dissection of the gastrocnemius–soleus junction.png|thumb|Dissection of the gastrocnemius–soleus MTJ]]
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 ==
* With aging there is shortening of the interdigitations with a resulting decrease in contact area between the sarcolemma and extracellular components.<ref>Wikimsk MTJ Available:https://wikimsk.org/wiki/Myotendinous_Junction (accessed 12.6.2022)</ref>
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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