To examine the macroscopic vascular pattern of early synovitis in psoriatic arthritis (PsA), reactive arthritis (ReA), and rheumatoid arthritis (RA) and to assess the reliability of the grading features for synovitis.
Forty-four patients (14 PsA, 12 ReA, and 18 RA) with knee synovitis who were undergoing arthroscopy were assessed. Video recordings of the examination were scored independently by 3 arthroscopists who were blinded to the patient's identity and clinical details. Features of vascularity, villous formation, pannus, granularity, and capillary hyperemia were recorded and kappa values (-1<kappa<1) were calculated to assess interobserver reliability.
The interobserver reliability between experienced observers was high (kappa> or =0.8) for features of vascularity, villous hypertrophy, and pannus. Seventy-three percent of the PsA and ReA patients had predominantly tortuous, bushy vessels; 89% of the RA patients had mainly straight, branching vessels.
The distinct vascular patterns in PsA and ReA compared with those in RA may reflect different specific vascular factors in the pathogenesis of these arthritides. Vascularity and villous hypertrophy are the most reliable features of synovitis grading.