Pisotriquetral arthritis: 'forgotten joint in ultrasound imaging of the wrist

We read with great interest the study of Di Matteo et al,1 which highlighted the association between ultrasound (US)-detected subclinical synovitis and bone erosion with the development of inflammatory arthritis. We agree with the authors that the second and fifth metacarpophalangeal joints and the fifth metatarsophalangeal joints are the most frequent site of US-detected bone erosion.2 However, MRI studies have reported that in rheumatoid arthritis (RA), carpal joints were affected by synovitis and erosions more frequently than metacarpophalangeal joints.3 4 The ulnar aspect of the radiocarpal joint and the pisotriquetral joint (PTJ) are the most involved by synovitis.5 Moreover, triquetrum is among the most frequent erosion-affected bone3 and, according to a recent MRI investigation, seems to be the first morphological site to be affected by RA.4

PTJ is a small joint of the ulnar side...