the present invention provides new formulations of injectable particles useful for intra - articular injection . the formulations are made of biocompatible polymers that biodegrade to generate nsaids , ad are useful for treating inflamed joints , thus providing safe , long - lasting relief of joint pain and swelling . in one embodiment , the present invention provides an injectable particle , comprising a biodegradable polymer comprising an agent selected from the group consisting of an nsaid , a cox - 2 inhibitor , an anesthetic and a narcotic analgesic .