The painful arc syndrome is characterized by pain in the shoulder and arm when lifting. This discomfort is caused by a mechanical blockage between the head of the humerus and the acromion process, called the subacromial space.
This is because the greater tuberosity of the humerus must enter under the acromial space and to achieve this, the humerus must rotate externally. If the arm does not rotate enough, the shoulder joint will be dysfunctional.
The following muscles are responsible for this movement:
- Supraspinous
- Infraspinatus
- Teres Minor Muscle
- Posterior deltoid
Tissue that can be compressed in the subacromial region:
- Subacromial bursitis, where the walls of the bursa are inflamed due to mechanical irritation.
- Calcified deposit in the supraspinatus tendon occurs when a calcareous deposit forms in the tendon, and the lesion is surrounded by a inflammatory reaction.
- Supraspinatus tendonitis which is an inflammatory reaction condition triggered by the degeneration of tendon fibers.
- Minor tears of the supraspinatus tendon usually causing an inflammatory reaction with local swelling.
The abduction movement is accomplished through the external rotation of the humerus. The humerus begins this movement between 40 and 60 degrees. So we’ll say the bow will hurt. The glenohumeral movement will then be dysfunctional.
Rounded shoulders:
This poor posture creates internal rotation of the humerus and this may be permanent if not corrected at a young age. With permanent internal rotation, it will be difficult to externally rotate the humerus to accommodate the greater tuberosity of the humerus. This person will be prone to suffer from arc of the humerus syndrome. Also the brachial nerve, the one near the head of the humerus, is more likely to be compressed.
