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Muscle Test: Deltoid

Exams and Signs
Origin:Anterior fibers:
Clavicle (shaft: anterior border and superior suface of lateral 1/2)
Middle fibers:
Scapula (acromion, lateral margin and superior surface)
Posterior fibers:
Scapula (spine on lower lip of posterior border)
Insertion:Humerus (deltoid tuberosity on lateral mid-shaft via humeral tendon)
Innervation:Cervical root(s): C5 and C6
Nerve: axillary nerve (ventral rami)

 

Grading of muscle strength:

Grade

Strength

Description

  5*

Normal

Completes full range of motion against maximal finger resistance

  4*

Good

Tolerates moderate resistance

3

Fair

Completes full range of motion with no resistance

2

Poor

Completes partial range of motion

1

Trace

Slight contractile activity

0

Zero

No contractile activity
*The distinction between Grades 4 and 5 is based on comparison with the normal hand and, barring that, extensive experience in testing the hand.

Testing

Anterior deltoid (shoulder flexion)
Position of patient
  • Short sitting with arms at sides, elbow slightly flexed, and forearm pronated
Examiner’s actions
  • Stands at test side; hand applying resistance is contoured over the distal Humerus just above the elbow; the other hand may stabilize the shoulder
Instructions for the patient
  • “Raise your arm forward to shoulder height. Hold it. Don’t let me push it down.”
Posterior deltoid (shoulder extension)
Position of patient
  • Prone with arms at sides and shoulder internally rotated (palm up)
Examiner’s actions
  • Stands at test side; hand applying resistance is contoured over the posterior arm just above the elbow
Instructions for the patient
  • “Lift your arm as high as you can. Hold it. Don’t let me push it down.”

 

Posterior deltoid (shoulder abduction, horizontal)
Position of patient
  • Prone with shoulder abducted to 90° and forearm off the edge of the table with elbow straight
Examiner’s actions
  • Stands at test side; hand applying resistance is contoured over the posterior arm just above the elbow
Instructions for the patient
  • “Lift your elbow up toward the ceiling. Hold it. Don’t let me push it down.”
Middle deltoid (shoulder abduction)
Position of patient
  • Short sitting with arm at side and elbow slightly flexed
Examiner’s actions
  • Stands behind the patient; hand applying resistance is contoured over the arm just above the elbow
Instructions for the patient
  • “Lift your arm out to the side to shoulder level. Hold it. Don’t let me push it down.”
Presentation Photos and Related Diagrams
  • Deltoid muscle
    Deltoid muscle
Definition of Positive Result
  • In muscle testing, a normal result is a positive one. During a normal muscle test, the examiner should observe a normal muscle contraction that can move the joint or tendon against full resistance.
Definition of Negative Result
  • In muscle testing, an abnormal result is a negative one. During an abnormal muscle test, the examiner should observe an abnormal muscle contraction that can move the joint or tendon. In a complete denervation injury, such as a complete nerve laceration, there will be no evidence of any muscle function and the muscle testing grade will be 0.
Comments and Pearls
  • Do not allow shoulder elevation or lateral flexion of the trunk to the opposite side because these movements will create the illusion of shoulder abduction.
  • If the shoulder is painful in abduction, especially with lifting, resisted external rotation is a good substitute exercise
  • The deltoid is innervated by C5
Diagnoses Associated with Exams and Signs
References
  1. Hislop JH, Avers D, Brown M. Daniels and Worthingham's Muscle Testing, Techniques of Manual Examination and Performance Testing. 9th ed. St. Louis, Missouri: Elsevier Saunders, 2014, pp. 138–202.
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