Osteoarthritis (OA) is the most common form of arthritis, affecting millions of people worldwide and it is common in an aging population. Surgical shoulder replacement (arthroplasty) is typically considered when non-surgical measures, such as physiotherapy or medication, have failed. There are two commonly performed surgical replacement procedures in patients who have advanced shoulder OA, and are 65 years of age and older: Total Shoulder replacement or Arthroplasty (TSA) and Reverse Total Shoulder Arthroplasty (RTSA). Few studies have compared the two procedures. Surgeons face uncertainty regarding which procedure to perform in patients 65 years of age and older. This pilot Randomized Controlled Trial (RCT) will compare the TSA and RTSA procedures, in patients 65 years of age and older. Participants will be assigned at random, (like flipping a coin), to one of the two groups (TSA or RTSA). The overall goal of this pilot study is to determine which procedure produces better functional and quality of life outcomes with fewer complications within the first 12-months after surgery. Moreover, pilot data will help determining the feasibility of conducting a larger trial comparing TSA versus RTSA surgical management in 65 years of age and older participants with advanced shoulder OA.