The purpose of this study is to compare the efficacy of intra-articular corticosteroid injections versus platelet-rich plasma injections for non-operative treatment of primary glenohumeral osteoarthritis. The efficacy of intra-articular injections, outside of hyaluronic acid, for the treatment of glenohumeral OA is not known, yet these treatments are commonly used with hopes of providing patients with symptomatic relief that can hopefully delay or prevent the need for shoulder arthroplasty. This study will help elucidate the therapeutic benefit of corticosteroid and Platelet Rich Plasma (PRP) injections in this patient population.