What is the function of Deltoid Muscle?

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The deltoid muscle is a big and thick muscle having a triangular course due to which the shoulder gets its contour and the molded shape. The triangular deltoid muscle name, originates from the Greek word, "deltoeides," which means  like a river delta. This muscle is considered as the main abductor of arm located at glenhumeral or shoulder joint and further flexes as well as moves up to the humerus. Deltoid muscle is considered as the most prominent muscle of the shoulder muscles and has deltoid ligaments attaching the muscle to the You do not have access to view this node.  It is capable of lateral, rotating and extending You do not have access to view this node.


What is the anatomy of the Deltoid muscle?

The deltoid muscle is divided on the basis of their origin and their position. In terms of the position, it is divided into three main portions: While the anterior and lateral muscles are originte from the collar You do not have access to view this node, the posterior originates on the Scapula.

  • Anterior muscles help in pectoral You do not have access to view this node
  • Lateral muscle helps in lateral You do not have access to view this node
  • Posterior muscle helps in extending You do not have access to view this node 

And on the basis of their origins and are divided into,

  • clavicular,
  • acromial and
  • scapular divisions.

These divisions of Deltoid muscles layer the proximal or upper part of humerus and converge to a thick tendon. It further gets inside the lateral humerus bone surface. All the three divisions of Deltoid muscle group have different structures and functions but work in synergy to enable main shoulder joint movements. Deltoid You do not have access to view this node has been known to give dynamic stability to the scapular plane during abduction process. The anterior fibers are present on the superior and anterior surfaces of external third of clavicle along with anterior acronium. The middle fibers are placed on the acronium’s lateral margin whereas the posterior fibers are situated on the scapular spine’s inferior edge. A convergence of thick tendon is formed by the anterior and posterior fibers and this thick tendon inserts on the humerus’s lateral surface close to the center point at deltoid tuberosity. The middle portion has a multipennate property and inserts with the help of 4 to 5 intramuscular septa or tendinous expansions.


How do the Deltiod muscles help in moving the hand?


The three divisions of the deltoid You do not have access to view this node sometimes contract together or even independently according to the need of the action. The three fibers and the actions performed by them are listed below:

Fibers                                           Action

Anterior fibers                            glenohumeral (shoulder) joint flexion, horizontal adduction, abduction in coronal plane and internal rotation

Middle Fibers                            Small part in flexion and key role in shoulder joint abduction

Posterior Fibers                      external rotation, glenohumeral joint extension, and abduction


What causes a trigger in the Deltoid muscle?

Impactful trauma like fall on the shoulder or direct blow or even extra stress or excess use of the Deltoid muscle can cause trigger points. The major difference in the activation of trigger points of Deltoid muscles as compared to other muscles is that the trigger points in these muscles is never concentrated to one remote area. Rather the pain intensifies more in the TrP area and erupts mostly when the shoulder movement takes place and the pain is usually not noticed while the body is at rest. If the pain is continuous in the shoulder area then it can be due to problem in some other muscles and not Deltoid You do not have access to view this node.


What is the treatment for Deltoid muscle disorders?

Never try to massage this part on your own as it is a very difficult position and the pressure won’t be applied properly. Use of tennis ball or lacrosse ball held against the wall and used for massaging the shoulder can certainly help. When more pressure is need even hard rubber bouncy type of ball can be used to massage the point of trigger.


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