Do you encounter patients experiencing persistent shoulder pain, limited range of motion, and dysfunction despite your efforts to restore glenohumeral joint mobility, restore anterior chest muscle flexibility, and improve rotator cuff strength? Feeling unsure about the next step? Have you thought about assessing and correcting pelvic alignment to address the issues?
Many shoulder dysfunctions are less related to soft tissue restrictions and glenohumeral joint hypomobility and more associated with forward shoulder posture, decreased scapular upward rotation, and changes in electromyographic (EMG) activity of the muscles responsible for scapular upward rotation.
Research demonstrates that isolated, traditional treatment approaches alone may not effectively address or improve shoulder pain, weakness, and dysfunction. Why might this be the case? It has to do with understanding a whole-body connection and how each part interconnects and coordinates with the others to assure optimal functioning.
While well intended, efforts to restore shoulder and scapula alignment through adjustments in the soft tissue (such as stretching the pectoralis minor and major and strengthening the scapular upward rotators) may have limited impact. The missing link may be an oversight of how nonadjacent segments affect shoulder posture and biomechanics.
Pelvic Position Effect on Scapula
Consider the position of the pelvis. An anterior tilt of the pelvis produces an increased lumbar lordosis which in turn contributes to increased thoracic kyphosis. An increased thoracic kyphosis leads to an increase in scapular anterior tilt and internal rotation. Keep in mind that the position of the socket (glenoid fossa) influences the mobility of the upper extremity.
In addition, excessive thoracic kyphosis leads to alterations in the EMG activity of the muscles responsible for upward rotation of the scapula. Consequently, adjustments in pelvic posture can impact the position and function of the shoulder complex.
Scapular Muscle Activity
Let’s talk about how scapular muscle activity is affected by posture. EMG studies demonstrate that increased anterior pelvic tilt boosts the activation of the upper trapezius while reducing the engagement of the lower trapezius and serratus anterior. Conversely, when the degree of anterior pelvic tilt is decreased, there is a notable rise in the activation of both the lower trapezius and serratus anterior and a slight decrease in upper trapezius activity. By providing a more balanced activation of all three supporting muscles, joints can operate optimally, providing greater strength and power, improved range of motion, and reduced pain and risk of injury.
The Scapulothoracic Joint
Next, let’s explore arthrokinematics. Scapulothoracic joint alignment is crucial for shoulder function, requiring optimal positioning to ensure stability and a full range of motion. Ideally, the thoracic is convex with the concave scapula abutting the ribs. An anterior pelvic tilt changes the mechanics of the diaphragm (see Figure A). This will affect upper rib movement and the convexity of the rib cage, resulting in decreased congruency in the joint (see Figure B) and leading to the inability to effectively engage the scapular muscles.
Bottom Line
When treating patients with shoulder pathologies or dysfunction, it is crucial to focus on restoring correct posture alignment. This intervention will help to correct scapular muscle imbalances, assure adequate scapulothoracic congruency, promote correct breathing mechanics, and improve thoracic posture.
References:
Murta BAJ, Santos TRT, Araujo PA, Resende RA, Ocarino JM. Influence of reducing anterior pelvic tilt on shoulder posture and the electromyographic activity of scapular upward rotators. Braz J Phys Ther. 2020 Mar-Apr;24(2):135-143. doi: 10.1016/j.bjpt.2019.02.002. Epub 2019 Feb 25. PMID: 30826186; PMCID: PMC7082681.
