The Importance of Scapular Function in Shoulder Health
The shoulder is one of the most mobile joints in the body, making it susceptible to dysfunction and injury, especially in athletes and individuals who engage in repetitive overhead movements. At the centre of this complex system is the scapula, often referred to as the "shoulder blade". Despite its crucial role in shoulder mechanics, the scapula is sometimes overlooked in discussions of shoulder health. Understanding how the scapula works and what happens when it becomes dysfunctional is essential for maintaining shoulder stability, preventing injuries, and optimising performance.
In this post, we’ll explore the importance of scapular function, the role of key muscles like the rhomboids, serratus anterior, and trapezius, and the factors that contribute to scapular dyskinesis (abnormal movement of the scapula). By understanding how the scapula supports shoulder mechanics, you'll be better equipped to appreciate the significance of strengthening these essential muscles.
Scapular Function and Muscle Interaction
The scapula plays a crucial role in facilitating optimal shoulder function. Its anatomy and biomechanics interact to produce efficient movement. However, when there is weakness or dysfunction in the scapular muscles, normal positioning and mechanics may become compromised. If the scapula cannot perform its stabilising role, shoulder function becomes inefficient, leading to decreased neuromuscular performance and a potential increase in the risk of injury to the glenohumeral joint (Paine & Voight, 1993).
A strong scapular musculature is especially important for overhead athletes, such as swimmers and tennis players. Proper scapular firing and control not only improve performance but also aid in injury prevention. Weakness in these key muscles can disrupt the biomechanics of the glenohumeral joint, placing excessive stress on the rotator cuff and anterior capsule (Paine & Voight, 1993).
Unlike other joints, the scapula has no direct bony articulation with the thorax, allowing for a wide range of movement—protraction, retraction, elevation, depression, anterior/posterior tilt, and internal/external as well as upward/downward rotation. The scapula is attached to the thorax through ligamentous connections at the acromioclavicular joint and by a suction mechanism created by the muscular attachments of the serratus anterior and subscapularis. This mechanism keeps the scapula in close proximity to the thorax, allowing it to glide smoothly during movement (Paine & Voight, 1993).
While many muscles help stabilise the scapula, the primary stabilisers include the serratus anterior, rhomboid major and minor, levator scapulae, and the trapezius muscles. The muscles of the rotator cuff—the supraspinatus, infraspinatus, teres minor, and subscapularis—are the primary protectors of the glenohumeral joint. These muscle groups work in synergy, co-contracting to anchor the scapula and guide its movement (Paine & Voight, 1993)..
The Rhomboids
The rhomboid muscles (Figure 1) play a vital role in scapular adduction or retraction, which involves drawing the scapula back towards the spine. When the rhomboids are weak, the scapula cannot fully retract, a movement essential for actions such as overhead throwing and swimming strokes like the crawl. Inability to fully retract the scapula during these movements can place additional stress on the anterior shoulder structures. During the follow-through phase of throwing, the rhomboids eccentrically contract to decelerate the arm, making their strength critical for any overhead arm movement. Therefore, strengthening the rhomboids should be prioritised, particularly in patients with anterior shoulder instability (Paine & Voight, 1993).
Figure 1. Rhomboid muscles |
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Reproduced from BioDigital Human https://www.biodigital.com/ |
The Serratus Anterior and Trapezius
Weakness in the scapulothoracic muscles can lead to abnormal scapular positioning, disrupting the scapulohumeral rhythm and contributing to general shoulder dysfunction (Paine & Voight, 1993). Two key muscles, the serratus anterior (Figure 2) and trapezius (Figure 3), work together to stabilise the scapula against the chest wall. The upper and lower trapezius, along with the serratus anterior and rhomboid muscles, control the scapula's upward and downward movements (Van Der Hoeven & Kibler, 2006). The serratus anterior and lower trapezius form an important upward rotation force couple, enabling acromial elevation.
Weakness or inhibition of the serratus anterior and lower trapezius is common and often leads to abnormal movement patterns, such as reduced shoulder abduction and secondary impingement (Paine & Voight, 1993).
Figure 2. Serratus anterior muscle | |
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Reproduced from BioDigital Human https://www.biodigital.com/ |
Figure 3. Trapezius muscle | |
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Reproduced from BioDigital Human https://www.biodigital.com/ |
Contributing Factors to Scapular Dyskinesis
Several factors may contribute to scapular dyskinesis (abnormal movement of the scapula). These include:
Bony causes, such as poor posture or previous fractures.
Joint issues, including acromioclavicular joint instability, arthrosis, or internal derangement of the glenohumeral joint.
Neurological factors, such as cervical radiculopathy or nerve palsy.
Soft tissue problems, including muscle tightness, intrinsic muscle issues, or altered activation of the periscapular muscles (Paine & Voight, 1993).
Many of these underlying causes of scapular dysfunction can be effectively addressed with a combination of acupuncture and osteopathic treatment. Osteopathy can restore joint stability and correct misalignments, while acupuncture stimulates healing and improves muscle function. Together, these therapies can provide both short-term pain relief and long-term improvement in scapular mechanics.
Conclusion
The scapula is integral to efficient shoulder function, and its proper movement and stability are crucial for athletes, particularly those involved in overhead sports like swimming and throwing. Weakness or dysfunction in the scapular muscles can lead to abnormal shoulder mechanics, increasing the risk of injury. By focusing on strengthening key muscles like the rhomboids, serratus anterior, and trapezius, we can optimise shoulder function and prevent many common shoulder issues.
Whether you're an athlete, fitness enthusiast, or someone recovering from shoulder injury, maintaining scapular health is essential. Incorporating targeted exercises to strengthen these stabilising muscles will help ensure proper shoulder mechanics and reduce the likelihood of dysfunction or injury.
References
Paine, R.M. and Voight, M., 1993. The Role of the Scapula. Journal of Orthopaedic & Sports Physical Therapy, 18(1), pp.386–391. https://doi.org/10.2519/jospt.1993.18.1.386.
Van Der Hoeven, H. and Kibler, W.B., 2006. Shoulder injuries in tennis players. British Journal of Sports Medicine, 40(5), pp.435–440. https://doi.org/10.1136/bjsm.2005.023218.
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