Given current demographic shifts, the number of older adults continues to grow, with almost half of patients over 65 being diagnosed with some form of arthritis. Rheumatic diseases pose unique diagnostic challenges in older patients due to the convergence of physiologic changes of aging, confounding difficulties to care, and atypical disease manifestations. This review summarizes the current published evidence to guide clinicians in evaluating geriatric patients with rheumatologic concerns, focusing on inflammatory arthritis. Using the background of epidemiologic data on various musculoskeletal diseases, clinical presentations, current diagnostic tests, and known physiologic changes of aging, this review highlights five diagnostic pitfalls in inflammatory polyarthritis among older patients. The pitfalls include: 1) broader differential diagnosis; 2) atypical presentations; 3) communication, cognitive, and social impairments; 4) the role of chronological vs. biological age; and 5) anchoring bias by assuming older adults are simply “older young adults”. These pitfalls are discussed in the context of geriatric principles such as the “hallmarks of aging” and the expected pathophysiologic changes of organ systems. Furthermore, the review discusses the strengths and weaknesses of diagnostic tests used in arthritis and introduces some of the geriatric assessment tools that systematically evaluate multimorbidity and geriatric syndromes. With familiarity of the potential diagnostic pitfalls, knowledge of both normal and pathologic aging processes, awareness of the difference between biological and chronological age, and the ability to use geriatric assessment tools to better characterize older patients, clinicians will be better able to diagnose and manage rheumatic conditions in this population.