For a long time, treatment of osteoarthritis (OA) has been limited to oral administration of analgesic and anti-inflammatory drugs, called symptoms-modifying OA drugs. The aim of this thesis was to investigate a new way of treating arthritic diseases by intra-articular injection. A disease-modifying OA drug, VX-745 was successfully encapsulated in poly(lactic) and poly(lactic-co-glycolic) acid particles. The in vivo bioactivity of the drug was demonstrated for the first time in this thesis following intra-articular administration. The retention of the drug delivery systems in the joint was observed for 6 weeks and the drug content was released over extended periods of time. The possibility to adjust the drug loading and to modulate the release kinetics render polymeric particles interesting for the delivery of poorly water soluble drugs for the treatment of chronic diseases.