The sonographic examination of the knee-joint can, in many pathological alterations of the knee-joint, supply additional informations. In the standardized ultrasound examination of the knee-joint ventral and dorsal sectional planes will be adjusted (4, 7, 14, 17). For the examination of the lesions of the anterior cruciate ligament direct adjustment techniques in the aere of origin of the anterior cruciate ligament (15, 16) and indirect examination methods are known (7, 8, 9, 20). While Hien chose a direct medial parapatellaric horizontal sagittal sectional plane in the course of the lig. patellae (8), we carry out our examination in a ventral infrapatellaric sagittal plane. The examinations were conducted with an ultrasound unit of the type Siemens Sonoline SL 2 with a linear transducer with a frequency of 5 MHz without a stand off pad. In the course of a prospective clinical examination an anteromedial test of stability of both knee-joints was conducted on 360 patients with the help of a sonographic Lachman-test. Two examination groups were formed: in group 1 60 patients with a arthroscopically secured lesion of the anterior cruciate ligament were registered and set against 300 probationers with "empty" anamnesis of the knee-joint of group 2. In the group of patients with a cruciate ligament injury a tibia translation of 5.3 mm in the Lachman-test was found; the side difference between the leg injured and the one uninjured amounted to 3.0 mm. In the control group the tibia translation amounted to 2.9 mm with a side difference of 0.9 mm.(ABSTRACT TRUNCATED AT 250 WORDS)