Kinesiology of the Shoulder and Scapula

Kinesiology of the Shoulder and Scapula:

By Brent Brookbush DPT, PT, MS, PES, CES, CSCS, ACSM H/FS


Scapulohumeral Rhythm: The actions of the shoulder are paired with actions of the scapula.  This serves to both increase the available range of motion of the upper extremity, and allows the glenoid fossa to be positioned in a more stable position in relation to the humeral head.  For example, shoulder abduction is accompanied by upward rotation – this increases the amount of gleno-humeral abduction available by moving the acromion process “out of the way,” and this positions the glenoid fossa partially under the humeral head providing mechanical stability to downward force.  The analysis below pairs each shoulder joint action with the accompanying scapular movement.



Shoulder Horizontal Adduction and Scapular Protraction:


Shoulder Horizontal Adduction (Horizontal Flexion)

  • Prime Mover: Pectoralis major
  • Synergists: Anterior deltoid
  • Antagonists: Posterior deltoid
  • Neutralizers: Posterior deltoid, infraspinatus, and teres minor neutralize internal rotation force created by the anterior deltoid and pectoralis major. Middle deltoid, latissimus dorsi, teres major, and coracobrachialis neutralize ancillary motion in the frontal plane.
  • Stabilizers: Rotator cuff – supraspinatus, infraspinatus, teres minor, subscapularis
  • Fixators: Scapular muscles, intrinsic stabilization subsystem, rectus abdominis, obliques, quadratus lumborum, erector spinae


Scapular Protraction

  • Prime Mover: Serratus anterior
  • Synergist: Pectoralis minor
  • Antagonist: Mid


Kinesiology of the Shoulder and Scapula — 38 Comments

  1. if i have 120 degree elevation in scapular plan and 30 degree of scapular upward rotartion how to calculatescapulohumeral rhythm??

    • Hey Huda,
      As far as I know, scapular humeral rhythm is a concept and due to the difficulty in measuring the amount of scapular upward rotation in degrees it is rarely measured. Generally, a 3/1 ratio is thought to be normal (60 degrees of upward rotation to 180 degrees of shoulder flexion or abduction). However, this ratio is not consistent throughout the entirety of rotation. For example, much less upward rotation occurs in the first 90 degrees of shoulder abduction than abduction above 90 degrees. Research has shown that the actual rhythm is a far more complicated relationship with various positions of “arm elevation” requiring different percentages of total scapular rotation.
      Experience and close observation with palpation of scapular borders are likely the most reliable assessment of optimal shoulder/scapular mechanics.
      Hope that answers your question,

  2. I am interested in Horizontal shoulder adduction due to my research in muscle synergy. The prime muscle, and the other supporter muscles (Synergists muscles, Stabilizer muscles, etc.) look fine here, however, what is the reference for this conclusion, any paper, etc.? I mean, I have seen other articles where for the Horizontal shoulder adduction, there are three defined muscles instead of one (e.g., Pectoralis major, Posterior deltoid, and latissimus dorsi). Can you help in explaining this point?

    • The references for this paper are from various readings (Neumann, Hollinshead’s, Norkin, etc.) an understanding of physics:
      Horizontal Adduction (as in a bench press or chest fly): May be performed by both the pectoralis major and anterior deltoid… but the latissimus dorsi does not have an angle of pull for this motion. The posterior deltoid would be an antagonist; being a horizontal abductor.
      Hope that helps,

    • The references for this paper are from various readings (Neumann, Hollinshead’s, Norkin, etc.) and an understanding of physics:
      Horizontal Adduction (as in a bench press or chest fly): May be performed by both the pectoralis major and anterior deltoid… but the latissimus dorsi does not have an angle of pull for this motion. The posterior deltoid would be an antagonist; being a horizontal abductor.
      Hope that helps,

  3. Hey Huda,
    I made a mistake in my previous post… it is a 2:1 ratio – humerus to scapular movement. (120 degrees of humerus movement and 60 degrees of scapular movement). My apologies… I need to refrain from answering posts so late at night :-)

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  5. I am looking to find the muscles responsible for internal rotation of the scapula and also to know whether this is the same as abduction of the scapula.

    Any help is greatly appreciated.


    • Internal Rotation of the Scapula? As in scapular winging? Winging may be seen as anterior tipping (sagittal plane motion around an x axis). The muscles responsible for this action are the pectoralis minor, upper trapezius, and levator scapulae.
      Internal rotation of the scapula around the acromioclavicular joint (transverse plane motion around a Y axis) is likely due to the scapula being pulled around the ribs during protraction (abduction) and anterior tipping and it is less likely that there are specific muscles responsible for this action.
      Hope that helps,

  6. Pingback: Pilates – Stablising your shoulder blades | What is Yoga? Yoga articles from Tirisula Yoga Teacher Training Masters and students

  7. Why do we say ‘Shoulder Horizontal Adduction?’ It is ‘Horizontal Flexion’. Why do we have two names for the same movement. Is it given a different name in different countries, or is it that we just cant decide? It’s just a gripe of mine!

    • Hey Lee,
      I think it is due to the two different terms accurately describing the movement. Flexion is a reduction in angle between two bones about a joint, were as adduction is a bone moving toward mid-line about a joint. Adding horizontal to these terms is simply an adjective to describe the plain. Since these joint actions generally occur at ball and socket joints were bones coming closer together may be less the case, I do prefer adduction since movement toward mid-line is easily visualized.
      Just my 2 cents,

  8. I have a question regarding “Shoulder Horizontal Adduction”
    This movement has a one degree of freedom that is only the actual visible movement, or two-degree of freedom: the one that is visible, in addition to invisible part of required internal rotation of the shoulder? in other words, in Shoulder Horizontal Adduction an internal rotation occur or not.

    • Hey Fady,
      Shoulder horizontal adduction defines a motion through one plane and does not include other joint motions. Although paired actions may occur at other joints (facet joints, the tib-fib joints, the tibiofemoral joint) the shoulder allows us the freedom to combine almost any pair of actions, save opposing actions. Horizontal adduction can be done with both internal and external rotation.

  9. I’m having shoulder/scapular pain during shoulder flexion. I have it when I get to my end range. An example of an exercise that causes pain, would be a pull up. The pain is located near the inferior angle of my scapula. I am also experiencing pain in an internally rotated position. An example of an exercise that causes pain would be the “second pull” of a Snatch. The pain is felt near my posterior head of my deltoid. And finally my shoulder/scapular pain is felt with my hands overhead as if I was forming a Y. I feel pain in the BOTTOM portion of a over head squat, as in the receiving position of the Snatch.
    Can someone help answer what might be causing this pain/discomfort? My chiropractor believes it is my subscapularis. Any help would be greatly appreciated.

    • Hey Andre,
      A little hard to tell from your description, but I will point you in a few directions.
      You need to consider the length/activity of your cervicoscapular muscles (levator scapulae, rhomboids, upper traps)…
      You may look at your pec minor activity/lentgh, thoracic spine mobility, serratus anterior strength..
      If your subscapularis is over-active/short and triggerpoint laden then your external rotators are likely underactive, this is often related to posterior delt trigger points as well…

      Hope that gives you some ideas.

    • Hey Jeff,
      As your pec major is an internal rotator and your pec minor is anterior tipper and downward rotator I would think that you have a decrease in pec activity with external rotation.

  10. For a project, I need to identify the 3 muscles (prime mover, synergist, and antagonist) involved in the close up movement of the rotation of the shoulder. The example given to me would be the motion while paddling a canoe. I am not sure what this type of rotation would be called (scapular upward rotation possibly)and then what 3 muscles would be the prime mover, synergist, and antagonist. Could you please help clarify for me these areas?

    • Hey Madi,
      I think your teacher owes you a better explanation. You need to know whether he/she is speaking of scapular or glenohumeral motion, and which part of the paddling movement they would like you to analyze.
      There is no such thing as “close-up rotation”, another term in need of explanation.

  11. Hello,

    I am trying to analyse the rotation movements occurring at the shoulder joint during the backstroke swimming technique. I have had a look at this information closely and I am still trying to see which one of the above fits best? Any help welcome, thank you :)

  12. Hi i would like to know your opinion about the best exercise for anterior deltoid. I using lateral raises but idealy i would like to use front raises for my volleyball athlets. Is any problem biomechanicly with frontal raises??

    • Hey Giorgos,
      The answer is – there could be… The front raise may impinge the supraspinatus tendon in the subacromial space, and while under normal condition this does not result in any issue; when you are dealing with overhead athletes who already face tremendous stresses and volume on their shoulders, this may not be a good idea. I would likely stick with sagittal plane push ups, standing cable presses, and scaption. It is very likely that scapular stabilization exercises are more important for your athletes than anything for the anterior delts.

  13. For your above break down of the movements: Internal and External Rotation, is the shoulder abducted or adducted? or are the muscles the same within the rotation no matter where the arm is extended?

    • Think out about from anatomical position (glenohumeral joint nuetral). Things would change slightly if you were abducted to 90 degrees.

  14. I am confused.
    Can you tell me which scapular motion accompanied with shoulder movement ?
    Shoulder Flexion, scapular____?
    Shoulder abduction, scapular____?
    Thank You

    • Sorry, I had hoped that this post would help clarify,
      Shoulder Flexion is accompanied by upward rotation (but may also be accompanied by posterior tipping at end range shoulder flexion, and may be accompanied by protraction during pushing motions)
      Shoulder Abduction is accompanied by upward rotation.

  15. Hello, I recently suffered some trauma to my trapezius muscle on my left side. As a result, I had an elevated scapula with some winging. I’ve had to be very careful about which exercises I used to rehab this injury, because a lot of my shoulder muscles tried to compensate for weakened trapezius (lower, in particle).

    Here’s my question: do you think that these other muscles will recover now, or do I need to target them specifically? I noticed that my levator scapula on my left side is often taut, and I have had painful spasms in this muscle. I do have a head-forward posture that I am working on correcting, as well. Thanks for the information and great site! I’ve looked at a lot of these sites during my rehabilitation period, and I feel that this was one of the better ones!

    • My first question would be… are you sure it is your trap and shoulder dysfunction, and not your neck and possibly a nerve impingement?
      It’s hard to know exactly what will help from your paragraph, but it has been my experience that you have to treat all structures in a compensation pattern if you want a return to optimal function.

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  17. My son is a pitcher. He suffered a grade 2 ac sprain and has some posterior labrum fraying. When he pitches he says his shoulder feels like it is slipping forward. What can he do to correct this?

    • Hey Mike,
      Look for my videos on External Rotator Activation Progressions, Serratus Anterior Activation Progressions, and Trapezius Activation. Your son is also going to want to integrate Reactive Activation for the Serratus Anterior, External Rotators and Trapezius.
      Hope that helps,
      Dr. B2

  18. I’m trying to improve my score on the apley test…I think my chronic neck pain is attributed to my asymmetric findings with apleys test…

    I created my own test: I place the palm of my hand on my belly button and I try to internally rotate my humerus…when I focus on stabilizing the scapula to test strictly scapulohumeral muscles I don’t notice much difference…however when I “let my scapulothoracic muscles help out” I notice an extreme difference…my “failing arm” on the apley test also fails on this test or at least it’s asymmetric to the rom I get with my “good arm”

    I have been trying everything to help correct this asymmetry…what do you recommend?

    • I should also note that I can force my arm to match the rom I get with my good arm….do you think that can mean possibly a motor control issue here and I need to work on activating a serratus anterior that is in ocoma?

      • Hmmmmm….
        It’s a little hard to tell exactly what is going on. Do you have a harder time reaching from below your scapula or above with the “weaker” arm?

  19. Pingback: Shoulder External Rotation: More Infraspinatus, Less Posterior Deltoid | Brent Brookbush

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