Unravelling the Etiology of Shoulder Osteoarthritis

Osteoarthritis (OA) is a progressive disease resulting from the degradation of synovial joint articular cartilage over time. The hallmark symptom is diffuse aching and progressive pain made worse with activity. Loss of range of motion and compromised function inevitably follow. This degenerative disease can affect the shoulder joint. When symptoms become refractory to conservative treatment such as anti-inflammatory medication, steroid injections, activity modification or physical therapy; surgery (total or reverse shoulder arthroplasty) may be considered. Idiopathic shoulder OA is typically characterized by posterior subluxation of the humeral head upon the glenoid and posterior bone loss. An imbalance in the application of forces applied to the proximal humerus by the posterior and anterior rotator cuff muscles has been postulated to be the leading cause of idiopathic shoulder OA. However, there is only preliminary evidence to support this theory and the etiology of this pattern of deformity is unknown. The theory the posterior humeral head subluxation is a precursor to OA is only supported by very low-level evidence and no longitudinal studies have been conducted. As a result, the cause and natural history of shoulder OA remains unknown. Research into this area is urgently needed to generate knowledge that will inform future treatments aimed at modifying and slowing the progression of shoulder OA and to reduce the need for shoulder replacement therapy. The aim of this project is to develop an understanding of the pathophysiology of shoulder OA.