Arthritis includes approximately 100 conditions that affect the joints and surrounding tissues. It is a leading cause of activity limitations, disability, and chronic pain, and is associated with dispensed opioid prescriptions, substantially contributing to health care costs. Combined 2019-2021 National Health Interview Survey data were analyzed to update national prevalence estimates of self-reported diagnosed arthritis. An estimated 21.2% (18.7% age-standardized) of U.S. adults aged ≥18 years (53.2 million) had diagnosed arthritis during this time frame. Age-standardized arthritis prevalences were higher among women (20.9%) than men (16.3%), among veterans (24.2%) than nonveterans (18.5%), and among non-Hispanic White (20.1%) than among Hispanic or Latino (14.7%) or non-Hispanic Asian adults (10.3%). Adults aged ≥45 years represent 88.3% of all U.S. adults with arthritis. Unadjusted arthritis prevalence was high among adults with chronic obstructive pulmonary disease (COPD) (57.6%), dementia (55.9%), a disability (54.8%), stroke (52.6%), heart disease (51.5%), diabetes (43.1%), or cancer (43.1%). Approximately one half of adults aged ≥65 years with COPD, dementia, stroke, heart disease, diabetes, or cancer also had a diagnosis of arthritis. These prevalence estimates can be used to guide public health policies and activities to increase equitable access to physical activity opportunities within the built environment and other arthritis-appropriate, evidence-based interventions.