OBJECTIVES: Osteoarthritis (OA) is the most common musculoskeletal disease, with around 1.6 million patients in Spain. The aim of this study was to determine health care resource utilization and direct medical costs of patients suffering OA of the hip, knee and wrist in Spain in 2009. METHODS: A cost-of-illness analyses was performed to estimate direct medical costs of patients suffering OA. Prevalence data on OA by the Spanish Society of Rheumatology showed a value of 18% for the Spanish population. A semi-structured questionnaire was sent to rheumatologists to collect data on health care resource utilization and costs. Inpatient costs were considered from the perspective of the public health care system. Direct medical costs included were ambulatory, diagnostic tests, physiotherapy, surgery, drug and administration costs. All costs referred to 2009. RESULTS: Patients diagnosed with OA of the hip, knee and wrist in Spain were estimated to be 1.6 million in 2009. Total medical costs for the Health Care System resulted as following: drug use 95€ million, health care personnel 251€ million, diagnostic tests 20€ million, physiotherapy 93€ million, surgery 105€ million and adverse effects due to OA medication 25€ million. Due to demographic changes and increasing prevalence, the number of patients is estimated to grow to 1.7 million with total costs of 717€ million in 2014. CONCLUSIONS: Direct medical costs for OA were estimated at 598€ million for Spanish patients in 2009. Health care personnel represented 43% of the total direct medical costs. Aging of the population, development of new drugs and increasing patient expectations are likely to increase the future economic impact of OA, which remains a major public health burden.