The present invention relates to a formulation sized for injection comprising a biodegradable polyesteramide co-polymer comprising at least a diol of bicyclic-1,4:3,6-dianhydrohexitol and analgesics for use in the treatment of arthritic disorders. More specific the invention relates to a formulation comprising injectable microparticle according to claim 1 wherein the polyesteramide co-polymer further comprises a diacid, a diol different from bicyclic-1,4:3,6-dianhydrohexitol and at least two different amino-acids. The formulation is used to treat pain or inflammation in a patient comprising administering to said patient a therapeutically effective amount of the formulation once or twice a year.