OBJECTIVES: The aim of the study is to estimate the pension costs (social security system in Italy is financed by public expenditure) induced by patients with musculoskeletal disorders (MD) and specifically for rheumatoid arthritis (RA), ankylosing spondylitis (AS) and psoriatic arthritis (PsA) in Italy, between 2009 and 2012. METHODS: We analysed the database of National Institute of Social Security (INPS) for three types of social security benefits: disability benefits, disability pensions (for people with reduced work ability) and incapacity pensions (for people without work ability). A probabilistic model with a Monte Carlo simulation was developed in order to estimate for MD, RA, AS and PsA, the total costs of the three types of benefits.. For the estimation of the productivity loss for RA in the 2012, economic data (cost of work day) were collected from the databases of the National Institute of Statistics (ISTAT) and absenteism data from national literature review (Censis, Anmar, SIR, 2008; Leardini 2002; Salaffi 2005). RESULTS: The model estimated a total costs of €311.534.554 ± €31.849.117 in the 2009 and €301.244.287 ± €33.871.230 in the 2012 for the disability benefits, €11.163.392 ± €3.047.946 in the 2009 and €10.560.086 ± €3.079.987 in the 2012 for the incapacity pensions and €136.473.625 ± €14.417.893 in the 2009 and €123.608.660 ± €13.734.418 in the 2012 for the disability pensions. The productivity loss for RA in the 2012 amounted to €1.145.377.593 ± €100.396.928. CONCLUSIONS: The most important indirect costs in Italy in 2012  was represented by disability benefits (68% of the total cost), followed by disability pensions (30% of total indirect cost). A better prescription appropriateness and rapid access to innovative treatments (Italy, among the EU Countries, is the one with the greatest delay in access) would reduce the costs incurred by the social security system accompanied by an improvement on the effectiveness of interventions.