Human Movement Science & Functional Anatomy of the:

Subclavius

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

The Subclavius Muscle - http://upload.wikimedia.org/wikipedia/commons/3/32/Subclavius_muscle_frontal3.png

What’s in a name

• Clavicle – Etymology: L, clavicula, little key (Medical Dictionary )
• Sub - word-forming element meaning "under, beneath; behind; from under; resulting from further division," from Latin preposition sub "under, below, beneath, at the foot of," also "close to, up to, towards;" of time, "within, during;" figuratively "subject to, in the power of;" also "a little, somewhat" (as in sub-horridus "somewhat rough"). (Etymology Online)
  • Muscle under the key-shaped bone

Origin of Subclavius - http://upload.wikimedia.org/wikipedia/commons/3/3d/Gray115.png

Origin: Attaches to the junction of the first rib with its cartilage, by a short thick tendon (8, 11).

Insertion: Inferior surface of middle 1/3 of clavicle in the "subclavian groove" (8, 11).

Insertion of Subclavius - http://upload.wikimedia.org/wikipedia/commons/f/f0/Gray201.png

Nerve: Subclavian nerve, arsing from the the junction of nerve roots C5 and C6 (11).

Note the "nerve to subclavius" originating from the junction of nerve roots C5 & C6 - http://upload.wikimedia.org/wikipedia/commons/thumb/0/0e/Brachial_plexus_2.svg/864px-Brachial_plexus_2.svg.png

Action:

• Clavicle: Anterior rotation, protraction and depression of the clavicle (8, 11)
  • In quadrupeds this muscle is larger and plays an important role in stabilization of the shoulder girdle for locomotion. In humans this muscle is a small, secondary muscle (14).
• Respiration: The subclavius may aid in forceful inspiration by elevating the first rib (14).

Note how the brachial plexus courses under the subclavius, but splits at the pectoralis minor.

Relative Location:

• The subclavius muscle is a deep muscle, with much of its mass lying behind or underneath the anterior face of the clavicle. The anterior face of the clavicle is deep to the pectoral fascia, pectoralis major and clavipectoral fascia. The subclavian neurovascular bundle passes inferior to the subclavius, including the subclavian artery and vein and the brachial plexus with a few exceptions (e.g. the long thoracic nerve, suprascapular nerve, nerve to the subclavius, etc.). Adaptive shortening and trigger point development of the subclavius may depress the scapula resulting in impingement/entrapment of the subclavian neurovascular bundle and is believed to be a contributing factor to radiculopathies and thoracic outlet syndrome (8). The subclavius makes up a portion of the anterior wall of the axilla that continues inferiorly via the clavipectoral fascia sheath that envelopes both the subclavius and pectoralis minor. The subclavian neurovascular bundle, lymph vessels, lymph nodes and adipose tissue lie deep to the subclavius in the axilla. The most medial attachment of the subclavius borders the attachment of the most superior fibers of the sternal head of the pectoralis major. The insertion and fascia enveloping the subclavius appears to run continuous with the conoid (coraco-clavicular) ligament.

Note how the subclavian vessels and brachial plexus course underneath the subclavius muscle - http://upload.wikimedia.org/wikipedia/commons/5/52/Slide10d.JPG

Palpation:

• The subclavius may be palpated through the fibers of the clavicular head of the pectoralis major.
  • To ensure the clavicular head of the pectoralis major is relaxed and "put on slack," have your partner lie on their side with their arm supported in slightly flexed, adducted and medially rotated position. Place your thumb at the center of the clavicle and try to gently roll your thumb through the thick pectoralis major fibers and under the clavicle. Although it may not be possible to identify a distinct muscle belly, you can feel a few dense fibers on the underside of the clavicle; your partner may report that these fibers are sensitive to pressure. When palpating the subclavius try to distinguish between the pectoralis major fibers running "down" toward the axilla and the subclavius fibers which run nearly parallel to the clavicle (11, 14).

Note the subclavius attached to the underside of the clavicle as part of the anterior wall of the axilla - http://webmedia.unmc.edu/medicine/todd/dissection/idg02pectoral/p0411axilla.jpg

Integrated Function:

• Stabilization: Stabilization of sternoclavicular joint
• Eccentrically Decelerates: Elevation, retraction, and posterior rotation of the clavicle, and potentially elevation of the first rib.
• Synergists:
  • The subclavius may work synergistically with the clavicular head of the pectoralis major (directly), and pectoralis minor  (indirectly) to depress, protract and anteriorly rotate the clavicle.
    • Depression of the clavicle may be a constituent of scapular depression, implying that the lower trapezius  may work synergistically with the muscles listed above during this motion.
    • Anterior roll of the clavicle may be a constituent of anterior tipping of the scapula, implying the upper trapezius and levator scapulae may work synergistically with the muscles listed above during this motion.
  • The subclavius may work synergistically with the rhomboids , pectoralis minor and levator scapulae  during downward rotation of the scapula via depression of the clavicle.

http://www.eorthopod.com/online-courses/online-courses/sites/default/files/images/shoulder_distal_clav_osteolysis_anatomy04.jpg

Arthrokinematics:

• All of the muscles that move the scapula have an affect on acromioclavicular (AC) and sternoclavicular (SC) arthrokinematics, but the relationships are indirect and may vary depending on the intended motion, synergies recruited, compensation patterns present, and potentially individual differences in the shape of joint surfaces (16) .
  • The AC Joint: The AC joint is primarily responsible for rotational movements (upward and downward rotation), and those movements that fine tune how the scapula lies on the rib cage (internal/external rotation and anterior/posterior tipping) (3).
    • To my knowledge, no study has directly examined the effect of the subclavius muscle on AC joint arthrokinematic motion. Based on common dysfunction, clinically effective mobilization techniques, and EMG studies discussed in previous articles (Trapezius , Rhomboids , Levator Scapulae , Pectoralis Minor , Serratus Anterior ) we may be able to assume that the AC joint follows convex on concave rules in the sagittal plane (slide opposite roll) and concave on convex rules in the frontal plane (slide follows roll). Relative to shoulder girdle and glenohumeral dysfunction, excessive downward rotation, anterior tipping and internal rotation of the scapula are common in those individuals with Upper Body Dysfunction (UBD) , and to aid in correcting impairment at the AC joint, many clinician's use posterior to anterior mobilizations and superior to inferior mobilizations applied on the distal clavicle. This could imply that the acromion has a propensity toward, inferior glide, anterior spin and increased compressive forces relative to the distal clavicle, and that pushing inferior and anterior on the clavicle relative to a stable scapula results in better congruence. A study by Lawrence et. al , did demonstrate less relative posterior rotation of the clavicle and less upward rotation of the scapula in those individuals with shoulder impingement (16).
    • Based on fiber direction and known osteokinematic motion, the subclavius would be capable of anterior spin, inferior glide and posterior glide of the clavicle on the acromion. Based on the model of AC joint dyskinesis above, inferior glide and anterior spin of the clavicle may actually improve joint congruence, as these motions would enhance alignment of joint surfaces in those who demonstrate anterior (spin) tipping and inferior glide of the acromion on the clavicle. In essence, the actions of the subclavius may counter dyskinesis at the AC joint by moving the clavicle in the same direction that the scapula has adopted in upper body compensatory patterns. Another way to view the contribution to arthrokinematics would be "relative motion", in which anterior spin of the clavicle is the same as posterior spin of the acromion, and inferior glide of the clavicle is the same as superior glide of the acromion (relative to arthrokinematic motion of the AC joint). Although this would imply that the subclavius should be activated/strengthened in those experiencing AC joint pain, I do not believe matching clavicular position to a scapula that has adopted a compensatory position is a viable option for treatment. I find it to be far more likely that the subclavius contributes to dyskinesis as an over-active structure by protracting, depressing and anteriorly rotating the clavicle to match the compensatory position adopted by the scapula. Initially, this would be beneficial to AC joint health due to a reduction in arthrokinematic dysfunction, and potentially stress on intra-articular structures. However, long-term this may result in a positive feedback loop, where changes in clavicular position and subclavius activity allow for greater anterior tipping and downward rotation of the scapula, and scapular position forces larger changes in clavicular position, etc. Very little has been written about subclavius activity and intervention, so further practice and future research is desperately needed.

http://upload.wikimedia.org/wikipedia/commons/f/f7/Subclavius_muscle_animation2.gif

• The Sternoclavicular Joint (SC): The SC joint allows motion in all three planes contributing to protraction/retraction in the transverse plane, elevation/depression in the frontal plane, and rotation along the clavicles longitudinal axis (3). As the SC joint is a saddle joint, convex on concave rules apply in the frontal plane (slide opposite roll), while concave on convex rules apply in the transverse plane (slide follows role) (3). Longitudinal rotation of the clavicle follows the direction of scapular tipping and would incorporate spin in the same direction at the proximal clavicle.
• Based on the fiber direction of this muscle and the nearly parallel arrangement to the clavicle, this muscle would seem to play a key role in SC joint stabilization via compression (3, 15). Further, its larger size and role in stabilization of the shoulder girdle during ambulation in quadrupeds would seem to support this notion.
• It's position underneath the clavicle would seem to imply a role in anterior rotation of the clavicle and anterior spin of the SC joint. As mentioned above, a lack of posterior rotation of the clavicle and a reduction in upward rotation of the scapula has been noted in individuals with impingement syndrome (16) . It is my hypothesis that the subclavius is the functional antagonist to the clavicular fibers of the upper trapezius . This may imply that inhibition of the upper trapezius results from altered reciprocal inhibition of the subclavius, or may result in over-activity of the subclavius due to adaptive shortening as a result of a change in clavicular and scapular position.

From Trapezius Article - It is my hypothesis that that the role of the upper trapezius in arthrokinematic motion of the AC joint is to ensure that both joint surfaces (clavicle and acromion) elevate simultaneously with the anterior fibers contributing to optimal clavicular posterior rotation during elevation of the arm.

The subclavius would oppose the "anterior/clavicular" fibers of the upper trapezius by depressing, anteriorly rotating and potentially protracting the clavicle. The affect on SC joint arthrokinematics would include anterior spin (or reduction in posterior spin),

• In previous articles (Trapezius , Rhomboids , Levator Scapulae , Pectoralis Minor , Serratus Anterior ) I have described arthrokinematic motion of the SC joint, in the frontal plane (superior and inferior glide), as acting much like a see-saw (teeter-totter). That is, depression of the distal end of the clavicle results in superior glide of the clavicle on the manubrium, and visa-versa. In the case of the subclavius, the muscle attaches to the medial third of the clavicle implying it may function as the fulcrum and have little if any affect on frontal plane SC joint arthrokinematics. Another hypothesis may consider the lateral/inferior to superior/medial slope of the joint surfaces, and propose that superior glide is paired with compression, and activity of the subclavius contributes to both. More research is needed to determine the actual arthrokinematic motion created by subclavius activity at the SC joint.

The articular surfaces of the sternoclavicular (SC) joint - Convex-on-Concave (slide opposite roll) in the frontal plane & Concave-on-Convex (slide follows roll) in the transverse plane - https://classconnection.s3.amazonaws.com/184/flashcards/1904184/png/11353978907868.png

Facial Integration:

My Fascial Hypothesis: Large fascial sheaths not only play a role in the transmission of mechanical force, but may also play a role in dictating the function of muscular synergies. This is likely caused by reducing or increasing tone of invested musculature via reflex arcs formed between mechanoreceptors embedded in the connective tissue and the attached musculature. In this way my view of fascia differs slightly from noted expert on the subject Tom Myers. I think of these large fascial sheaths (specifically the thoracolumbar fascia, iliotibial band, and abdominal fascial sheath) as natures “mother board.” A place for mechanical information to be communicated to the nervous system for more efficient recruitment of the muscular system. Despite having a slightly different philosophy it does not change the fact that fascia plays an important communicative role in the human body and we have Tom Myers to thank for his work.

The fascial network between fascicles of a muscle - http://www.selfcare4rsi.com/online-courses/online-courses/images/fascia.jpg

• Origin: The origin of the subclavius borders the origin of the upper most fibers of the sternal head of the pectoralis major on the first rib. If it was not for the separate neural innervation and separation from the pectoralis major by the clavipectoral fascia this muscle may have been viewed as an outcropping of the pectoralis major itself (similar to the articularis genu and vastus intermedius ). The trigger point referral pattern (see below) for the subclavius is similar to the pectoralis major implying some sensory continuity, although specific research is needed to explore this relationship further. Functionally, the subclavius and the most superior sternal fibers of the pectoralis major would compress, anteriorly rotate, depress and protract the clavicle, although the pectoralis major acts indirectly via the glenohumeral joint.

Deep Front Arm Line - left arm of image on right (deeper musculature on anterior view) - http://api.ning.com/online-courses/online-courses/files/zogvUtrhf2tc4xTJccfZ1YxH93z*4aeDC9sIcIjkkqO-n0c0roOISv*HCCYsb0G4tG78otJz7SDv1WQM1uHQ3PEVHLZNJErf/TomMyersAnatomyTrainsDFAL.png?width=750

• Insertion: The tendinous insertion of the subclavius appears to continue into the conoid (coraco-clavicular) ligament, and onto the coracoid process, implying a potential fascial relationship with the pectoralis minor , coracobrachialis and long head of the biceps brachii. Further, the subclavius is enveloped by the clavipectoral fascia, which continues to envelop the pectoralis minor (making up the anterior wall of the axilla). Tom Myers briefly mentions the subclavius as part of the Deep Front Arm Line (6). An example of these muscles working in concert, is likely best demonstrated when an individual is hanging, as in a pull-up . However, it is likely more pertinent to think of this fascial line relative to upper body dysfunction (UBD)  and the unfortunate posture adopted by desk workers. When one sits at a computer all of these muscles, as well as the clavipectoral fascia are maintained in a shortened position. Clinically, I have found all of these muscles are commonly over-active/short and prone to trigger point development, and the application of instrument assisted soft tissue mobilization (IASTM) to this fascial network results in positive changes in mobility. The adaptive shortening of this myofascial synergy may be one potential cause for the prevalence of upper body dysfunction (UBD) , and imply that more attention should be paid to innovating techniques for returning optimal myofascial extensibility.

Great cadaver disection with the subclavius muscle highlighted in green. (Pectoralis Major removed) - http://upload.wikimedia.org/wikipedia/commons/f/fb/Slide7b.JPG

Behavior in Postural Dysfunction:

The subclavius is likely short and over-active based on its contribution to osteokinematics and arthrokinematics and patterns of upper body dysfunction; however, very little has been written to support this hypothesis. Further research and clinical observations are needed.

In Upper Body Dysfunction (UBD) –

The subclavius is likely short and over-active in those individuals exhibiting Upper Body Dysfunction (UBD) . This assumption is based on the common shoulder girdle dysfunction associated with this compensatory pattern, including excessive anterior rotation of the clavicle and excessive anterior tipping and downward rotation of the scapula. In particular, the contribution of the subclavius to anterior spin of the clavicle is noteworthy, as the study mentioned above by Lawrence et al. (16)  demonstrated a decrease in posterior rotation of the clavicle in those with shoulder pain. Further, the subclavius may be the functional antagonist to the clavicular fibers of the upper trapezius  - a muscle with a propensity to become long and under-active. Most often, functional antagonists demonstrate opposing changes in muscle length and activity in individuals exhibiting compensatory patterns.

In Lumbo Pelvic Hip Complex Dysfunction (LPHCD) and Sacroiliac Joint Dysfunction (SIJD)  the serratus anterior plays no significant role.

In Lower Leg Dysfunction (LLD)  the serratus anterior plays no significant role.

In Short, the subclavius may have a propensity toward over-activity and adaptive shortening in upper body dysfunction (UBD) . This implies that release, lengthening and mobilization techniques specific to the subclavius and SC joint should be part of a human movement professional's repertoire. Due to the deep location of this muscle and the inherent issues with self-mobilization of the SC joint, this may be a muscle best assessed and treated by licensed professionals (PT, ATC, DC, OT, DO). Lengthening of the muscle could likely be achieved using a child's pose or crucifixion stretch (videos below).

Clinical Implications:

• Impingement of subclavian neurovascular bundle (thoracic outlet syndrome?)
• Subclavius trigger points
• AC Joint Pain
• SC Joint Pain
• Upper extremity radiculopathy (Brachial plexus impingement)
• Shoulder impingement
• Bursitis
• Thoracic Outlet Syndrome
• Osteoarthritis
  • AC Joint
  • SC Joint
  • Glenohumeral Joint

Signs of Altered Length/Tension and Tone:

• Overhead Squat:
  • Arms Fall - Short/Over-active
  • Shoulder Girdle Elevation - Short/over-active
• Special Tests:
  • Thoracic Outlet Syndrome
    • Roo's Test
    • Adson's Test
    • Wright Test
• Passive Accessory Movements
  • SC Joint Stiffness
  • AC Joint Stiffness

Subclavius Trigger Points:

• Palpation results in tenderness and may result in radiating symptoms.

Subclavius Trigger Point and Referral Pain Pattern - http://www.triggerpoints.net/sites/default/files/styles/triggerpoint_display_for_muscle_pages/public/Subclavius.jpg?itok=Nuq1t6eo

Recommended techniques for optimizing subclavius length & activity:

1. Manual Release of Subclavius
2. Inferior glide of clavicle at SC joint
3. Posterior to anterior mobilization of the AC joint
4. Crucifixion Stretch
5. Child's Pose

Crucifixion Stretch

Child's Pose Stretch

Bibliography:

1. Phillip Page, Clare Frank , Robert Lardner , Assessment and Treatment of Muscle Imbalance: The Janda Approach © 2010 Benchmark Physical Therapy, Inc., Clare C. Frank, and Robert Lardner
2. Dr. Mike Clark & Scott Lucette, “NASM Essentials of Corrective Exercise Training” © 2011 Lippincott Williams & Wilkins
3. Donald A. Neumann, “Kinesiology of the Musculoskeletal System: Foundations of Rehabilitation – 2nd Edition” © 2012 Mosby, Inc.
4. Michael A. Clark, Scott C. Lucett, NASM Essentials of Personal Training: 4th Edition, © 2011 Lippincott Williams and Wilkins
5. Leon Chaitow, Muscle Energy Techniques: Third Edition, © Elsevier 2007
6. Tom Myers, Anatomy Trains: Second Edition. © Elsevier Limited 2009
7. Shirley A Sahrmann, Diagnoses and Treatment of Movement Impairment Syndromes, © 2002 Mosby Inc.
8. David G. Simons, Janet Travell, Lois S. Simons, Travell & Simmons’ Myofascial Pain and Dysfunction, The Trigger Point Manual, Volume 1. Upper Half of Body: Second Edition,© 1999 Williams and Wilkens
9. Cynthia C. Norkin, D. Joyce White, Measurement of Joint Motion: A Guide to Goniometry – Third Edition. © 2003 by F.A. Davis Company
10. Cynthia C. Norkin, Pamela K. Levangie, Joint Structure and Function: A Comprehensive Analysis: Fifth Edition © 2011 F.A. Davis Company
11. Florence Peterson Kendall, Elizabeth Kendall McCreary, Patricia Geise Provance, Mary McIntyre Rodgers, William Anthony Romani, Muscles: Testing and Function with Posture and Pain: Fifth Edition © 2005 Lippincott Williams & Wilkins
12. Karel Lewit. Manipulative Therapy: Musuloskeletal Medicine © 2007 Elsevier
13. Carolyn Richardson, Paul Hodges, Julie Hides. Therapeutic Exercise for Lumbo Pelvic Stabilization – A Motor Control Approach for the Treatment and Prevention of Low Back Pain: 2nd Edition (c) Elsevier Limited, 2004
14. Andrew Biel, Trail Guide to the Human Body: 4th Edition, © 2010
15. David B. Jenkins, Hollinshead's Functional Anatomy of the Limbs and Back: Eighth Edition © 2002 Saunders
16. Lawrence, R. L., Braman, J. P., Laprade, R. F., & Ludewig, P. M. (2014). Comparison of 3-dimensional shoulder complex kinematics in individuals with and without shoulder pain, part 1: sternoclavicular, acromioclavicular, and scapulothoracic joints. journal of orthopaedic & sports physical therapy, 44(9), 636-A8.

© 2015 Brent Brookbush

Questions, comments, and criticisms are welcome and encouraged.