Hip and knee osteoarthritis (OA) is a common cause of disability, with great quality of life and economic impact, hence the need for effective treatment. Patient satisfaction with treatment is a measure of therapeutic effectiveness and may be used to assess treatment switch in OA patients. A 3-month multicenter, prospective, epidemiologic, non-interventional study was conducted in patients with hip and/or knee OA to assess therapeutic efficacy in patients requiring treatment switch due to lack of effectiveness and/or tolerability in primary care settings. Therapeutic effectiveness was assessed by patient satisfaction using the osteoARthritis Treatment Satisfaction (ARTS) scale. The 3-month disease change [by the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and a pain visual analog scale (VAS)] and its correlation with treatment satisfaction were also assessed, as well as patient gastrointestinal (GI) and cardiovascular (CV) profiles. 5,976 patients were analyzed (mean age 68.8 years, 65.1 % female). 67 and 61.8 % showed high GI and CV risk, respectively. The proportion of patients on acetaminophen treatment during the study decreased from 74.8 % at baseline to 23.9 %, while the proportion on non-steroidal anti-inflammatory drugs (NSAIDs) increased from 59.8 to 85.8 %. At 3 months, the standardized (0-100) overall ARTS score increased from 57.7 to 71.6 (p < 0.0001), while disease severity decreased. There was a significant (p < 0.0001) negative association between the ARTS, and the WOMAC and VAS scores. Treatment switching from acetaminophen to NSAIDs as a consequence of poor effectiveness and/or tolerability resulted in increased patient satisfaction with treatment and lower OA severity.