OBJECTIVES: We describe pain level, medication use, potential medication-related events, perceived medication effectiveness, and medication switching among osteoarthritis (OA) patients. METHODS: 4,386 patients with self-reported OA completed an internet survey. Recent OA pain level was reported on a 0-10 scale (10 = "worst possible" pain). Respondents reported regular Rx and OTC medication use (~{!]~} 3x/wk), perceived medication effectiveness, and frequency of 6 conditions possibly associated with OA treatment(s) such as diarrhea, nausea/vomiting, heartburn, stomach pain, headache, and dizziness. Categorical frequencies were conservatively converted to continuous variables (e.g., 1-3x a month = 1/month) to facilitate estimation. Statistical comparisons were made using student's t tests, X2, and ANOVA. Logistic regression was used to identify predictors of medication switching. RESULTS: Demographics: Mean age 55.3 years, 70.8% female, 91.4% white. Average recent OA pain was 4.9; 70.1% reported pain in 3 joints. 28.0%, 27.8%, and 32.2% reported taking only OTC, only Rx, or both on a regular basis, respectively. 25.0% felt their OA medications were slightly or not effective; 54.1% felt they were only moderately effective. A total of 34.4% switched or discontinued medication(s) during the past year; 41.5% and 35.1% of these patients cited lack of effectiveness and/or side-effects as a reason, respectively. Respondents using both Rx and OTC OA medications experienced potentially medication-related events more frequently than those not taking medication. Patients who switched OA medications reported experiencing higher recent OA pain, GI events (compared to non-GI), pain in more than 6 joints, and more than 3 events potentially related to medication use and were more likely to be female ( all p = 0.05). CONCLUSIONS: The burden of OA on patients in terms of pain, medication use, and potential side effects is high. Only 1 in 4 patients in our sample perceived their OA medications to be effective, and most reported experiencing at least some OA pain despite regular medication use.