Diagnosis of acute knee ligament injuries: the value of stress radiography compared with clinical examination, stability under anaesthesia and arthroscopic or operative findings.

A consecutive series of 85 stress radiographic examinations was performed in order to evaluate the clinical reliability and use of stress radiography in disclosing acute knee ligament injuries. Eighty-three examinations were performed within one week of the injury. Sagittal stress examination discovered 27% of the 37 anterior cruciate ligament (ACL) tears and all four posterior cruciate tears. Valgus stress detected 56% of the medial collateral tears. The specificity of stress radiography was even reduced by the number of false positive stress results (n = 25) in posterior drawer or valgus-varus examinations. An ACL tear was, however, an isolated or major ligament injury in twenty (80%) of the false positive results. Clinical examination revealed all the medial collateral tears whereas only 40% of the anterior cruciate tears. The most reliable method for diagnosing acute knee injuries where clinical examination has failed in disclosing instability is examination under anaesthesia supplemented by acute arthroscopy.