In fifteen cadaver wrists and ten foetus wrists palmar ligaments were studied. As a result, the palmar scapho-triquetral ligament was presented by means of gross anatomical study, MR imaging, and histological study. A kinematic study was conducted on three cadaver wrists to analyze patterns of motion on the proximal carpal row bones based on the helical axis concept. Motion analysis showed that the scaphoid has a set of helical axes bundled at the radial side of the wrist. On the contrary, the triquetrum had axes bundled on the ulnar side, approximately in the same position as the lunate. That shows that the lunate and triquetrum are coordinated in motion and opposed to that of the scaphoid. The structure possibly ruling this pattern of motion could be the palmar scapho-triquetral ligament, whose insertions on the scaphoid and triquetrum are close to the crossing-point of the helical axes of the scaphoid and triquetrum/lunate, respectively. In order to study the clinical relevance of our findings, a prospective clinical study on 53 patients after wrist injury was conducted. All patients were clinically examined, simple and semi-stress X-rays were taken, and arthrography and arthroscopy performed. Ligament tears were often found, but any correlation to clinical findings or arthrography could not be found. However, high correlation could be found between the lesion of the palmar scapho-triquetral ligament and a DISI position of the lunate combined with increased scapho-lunate angle. It can be concluded that the tear of the palmar scapho-triquetral ligament causes instability pattern that is radiologically evident at an early stage.(ABSTRACT TRUNCATED AT 250 WORDS)