Activated macrophages play a vital role in rheumatoid arthritis (RA) pathophysiology. CD44 is an overexpressed receptor on activated macrophages that is a potential target site for RA treatment. In this study, we prepared hyaluronic acid (HA) coated acid-sensitive polymeric nanoparticles (HAPNPs) composed of egg phosphatidylcholine, polyethylenimine, and poly (cyclohexane-1,4-diyl acetone dimethylene ketal) (PCADK) loaded with dexamethasone (Dex) for the treatment of RA. PCADK was used to form polymeric cores because of its acid-sensitivity. The HAPNPs were about 150 nm in size and had a zeta potential of −2.84 mV. The release rate of Dex from HAPNPs/Dex in vitro increased markedly when the pH decreased from 7.4 to 4.5, indicating that the HAPNPs were pH-sensitive. In a cellular uptake study, stronger fluorescence signals were observed in activated macrophages treated with HAPNPs, suggesting that HAPNPs could be effective nanodevices target to activated macrophages. In rats with adjuvant-induced arthritis, HAPNPs could inhibited the progression of RA. Taken together, these results suggest that the HAPNPs could be useful in RA therapy.