<p>Piroxicam is a non-steroidal anti-inflammatory drug which is used topically as an adjunctive treatment of knee osteoarthritis and as an option to control joint pain in patients suffering rheumatoid arthritis. In this study, an emulgel containing optimized nano-niosomal piroxicam was formulated and characterized in terms of mean size, polydispersity index, zeta potential, drug entrapment efficiency and capacity, release and transdermal permeation. Also, animal studies including pain level assessment, synovial prostaglandin E2 levels, knee joint swelling degree and histopathologic investigations were conducted. A randomized double-blind clinical trial was also performed to compare the analgesic effect of nano-niosomal piroxicam emulgel with piroxicam gel. The results showed optimized niosome formulation with 142 ± 7nm mean size and 0.23 ± 0.08 PDI, entrapped 99.48 ± 0.79% of added piroxicam with a sustained release pattern. Permeation studies indicated a 3.31-fold transdermal permeation of niosomal piroxicam emulgel compared with the piroxicam gel. The niosomal formulation significantly reduced knee joint swelling and prostaglandin E2 levels. The clinical trial indicated that the painkilling efficiency of the niosomal piroxicam emulgel was 37.30-fold and 3.16-fold greater compared to the placebo and the positive control groups, respectively. In conclusion, the niosomal piroxicam emulgel which may enable the drug to permeate through the skin and accumulate in synovial tissue more efficiently, showed a promising performance in lowering pain and inflammation based on the animal studies and the human clinical trial.</p> Graphical Abstract <p></p>