Shoulder pain is second only to back pain for visits to a doctor. The good thing is that evidence-based chiropractors are uniquely positioned to treat shoulder dysfunction better and faster than any other health care professional. Not because we are gurus, but because the research supports our approach. Manual therapy, ADL advice, joint manipulation, and specific rehabilitation are proven methods to reduce shoulder pain. Tissue injury and the resultant pain are consequences of sustained compression or repetitive stress to sub-acromial structures in nearly all shoulder pathologies. Two primary factors resulting in tissue injury are:
Nearly 100% of non-traumatic shoulder pain is due to these two factors!
The glenohumeral joint is designed to have significant ranges in all three planes of motion. Unfortunately, increased mobility comes at the expense of stability. The head of the humerus is a round structure contacting the minimally concave surface of the glenoid. Normal scapulohumeral motion maintains the humeral center of rotation directly above the concave scapular glenoid throughout the shoulders range of motion. This integrated motion between the scapula and humerus provides efficient function and joint stability. When this rhythm is disrupted by abnormal scapular motion, the resulting disproportionate humeral shift creates increased stress on the shoulder capsule and rotator cuff.
Scapular Dyskinesis leads to Shoulder Impingement creating Rotator Cuff Tendinopathy and resultant Rotator Cuff Tears
Rotator cuff dysfunction is now considered more degenerative than inflammatory– wherein a typical inflammatory reaction is histologically absent. Instead, there is degenerated and disorganized collagen fibers; signs associated with a failed healing response. Rotator cuff tendon degeneration may precede impingement in a self-perpetuating cycle of dysfunction. The process starts when an insult damages the tendon and leads to tendon degeneration. This weakens the tendon and diminishes its ability to oppose superior shearing force produced by the deltoid during arm abduction. The tendon becomes impinged, producing further insult. As tendon fibers fail, the enduring fibers remain under tension, thereby increasing the load and likelihood of failure.
Stress to the coracoacromial ligament (CAL) due to uncontrolled superior migration of the humeral head also results in calcification. The coracoid and acromion act as a roof the humerus. That’s right, type II and III acromions occur secondary to glenohumeral instability. Surgery to remove the acromion results in poor long-term outcomes as this further destabilizes the shoulder.
Function precedes structure until ultimately structure determines function. Wang et al. (2019) found increased coracoacromial ligament deformation and thickening of the supraspinatus in an overhead athlete population secondary to shoulder instability.
Cliff Atwell, B.S., D.C.