Mono-arthritis depicted a diagnostic challenge to even the most trained clinician; it is almost always probable to recognize patients who require vigorous determination and treatment to prevent rapid disease progression, such as those with suspected septic arthritis. The symptom of joint pain is related to a variety of disorders.

The initial step in determining the patient with monoarticular pain is finding out that the origin of the pain is the joint, rather than the nearby soft tissues. To study the joint distribution and 2-year outcome of patients with recent-onset monoarthritis. Adult patients with clinically apparent monoarthritis of ≤16 weeks' period were involved in a multi-centre 2-year longitudinal study. Clinical characteristics, joint distribution, the occurrence of chronic inflammatory rheumatic disease (CIRD), as well as classification conforming to the 2010 ACR/EULAR classification criteria for rheumatoid arthritis (2010 RA criteria), were determined. Multivariable logistic regression analyses analysed predictors for development of CIRD. The knee (49.3%), ankle (16.7%) and wrist (14.1%) were the most frequently affected joints among the 347 involved patients. Ninety-one patients (26.2%) grown-up CIRD during follow-up; 21 (6.1%) were recognised with rheumatoid arthritis and 16 (4.6%) with psoriatic arthritis. The more prolonged period of joint swelling, joint localisation, and ACPA- and RF positivity were independent predictors of CIRD. 21 of 49 (42.9%) patients with wrist monoarthritis and six of 58 (10.3%) patients with ankle monoarthritis grown-up CIRD through follow-up. The 2010 RA criteria recorded all patients detected with seropositive RA at an early stage, mostly within three months. Approximately one-fourth of patients with recent-onset monoarthritis grown-up CIRD over two years. Patients presenting with ankle arthritis rarely grown CIRD, whereas patients presenting with wrist arthritis continuously did so.  The prolonged period of joint swelling and ACPA- and RF positivity were also prognostic of CIRD. The evaluated data promote early identification of monoarthritis patients with unfavourable prognosis.