Rheumatoid arthritis (RA) is among the most disabling form of chronic inflammatory joint disease. Not all forms of arthritis develop into RA; on the contrary, it may be very challenging to differentiate RA from cases of arthritis that are self-limiting or caused by another disease. Evaluation of early arthritis includes some basic steps, such as excluding trauma, crystal, or infectious-related disease, as well as considering additional features that may guide towards a specific diagnosis. If no specific diagnosis can then be made, the presentation can be labelled as undifferentiated arthritis. Typical differential diagnoses of RA include viral polyarthritis, seronegative spondylarthropathies, polymyalgia rheumatic, and other systemic rheumatic diseases. In 2010, new classification criteria were published that led to a change in the approach to RA. Compared to the previous criteria, the American College of Rheumatology (ACR) 1987 criteria, a scoring system was devised, appreciating the type and number of affected joints (up to 5 points), as well as serology (up to 3 points), elevated acute-phase reactants (1 point), and a symptom persistence of 6 weeks or longer (1 point). If 6 or more points are reached, then classifiable RA is present. Importantly, classification status, which is used for study purposes, is not always identical to the diagnostic status, which often leads to clinical treatment.