Psoriatic arthritis (PsA) is an important condition that significantly impacts affected patients. The introduction of novel therapeutic agents for PsA has generated great interest in clinical trials as well as in clinical care. Therefore, there is a great need for standardized outcome measures that can accurately assess the activity of disease and response to therapy. Because it is a heterogeneous and multifaceted condition, defining outcome measures has been a challenge. To date, such measures have largely been adapted from other similar diseases. With further research, the most appropriate outcome measures specific for PsA will be delineated.