Contraction of developing avian heart muscle

26 patients with at least one clinical symptom that could indicate a tear of the scapho-lunate interosseous ligament but normal static and dynamic radiographs were examined by arthroscopy. We found that a diagnosis of scapho-lunate instability could be established by dynamic manoeuvres during radio-carpal and mid-carpal arthroscopy. Five patients were found to have true scapholunate instability. Six tears of the interosseous ligament without instability were also detected but it was doubtful if the tear was the origin of the painful symptomatology. This experience suggests that dynamic manoeuvres during arthroscopy are superior to other methods in diagnosing scapholunate instabilities at the pre-radiographic stage.