OBJECTIVES: To estimate the prevalence of shoulder osteoarthritis (OA) and its treatments. METHODS: Data from Thomson MarketScan (2005-2008), a large national managed care population database representing more than 500 million employer-based medical and pharmacy claims were analyzed.  Annual prevalence was calculated as the number of continuously eligible patients who had at least one shoulder OA diagnosis divided by the total number of continuously eligible patients.  Treatment prevalence was assessed for inpatient shoulder surgery, steroid injections, physical therapy and pain medication and was calculated as the number of patients receiving these treatment divided by the number of patients with a shoulder OA diagnosis.  Prevalence percentages were presented descriptively by age group and overall. RESULTS: There were approximately 20 to 26 million continuously eligible patients in the data annually between 2005 and 2008. The overall prevalence of patients with at least one shoulder OA diagnosis was relatively stable over the years and ranged from 1.1 to 1.2%.  In 2008, the shoulder OA prevalence by age group was: 0 to <18 – 0.01%; 18 to <40 – 0.21%; 40 to <65 – 1.55%; and 65 and greater – 4.16%. Shoulder surgery was most prevalent in the 40 to <65 age group (~1%), with around 2% prevalence in the 65 and greater age group.  Physical therapy was most common in the <65 year old groups (16.2% to 14.8%), while 65 and older age group had around 8% prevalence.  Steroid injections occurred in ~10% of the patients who were 18 or greater. Use of pain medications increased with age and ranged by age group from ~ 5% to 36%. CONCLUSIONS: The prevalence of a shoulder OA diagnosis was approximately 1.1%, with patients >65 age having the highest prevalence (>4%).  Shoulder OA treatment related resource utilization showed significant use of drug therapy, physical therapy, and steroid use.