Injuries of anterior cruciate ligament are constantly present in sports, but also in common life activities. Diagnostic procedures which are available today in diagnosis and estimation of severity of intraarticular knee structures, are numerous, but they are not available, plausibile and valid in the same manner. Aim of this study was to compare diagnostic validity of clinic and ultrasound examination related to arthroscopy in "fresh trauma: of anterior cruciate ligament This prospective study contains analysis 205 hospitalised patients treated from 2004 to 2006 at IOS "Banjica" Beograd and SOSH "Decedra" Beograd in matter of arthroscopy. Before the arthroscopy, clinical and ultrasound examination was performed. Values of sensitivity(87.1%), specificity(97.7%), positive (98.2%) and negative predictive value (84.3%) of ultrasound examination are affirmative in high reliability of this diagnostic procedure in a diagnosis of fresh lesions of anterior cruciate ligament.