Aim: The purpose of the study was to improve the ultrasonographic assessment of the anterior cruciate ligament by an inclusion of a dynamic element. The proposed functional modification aims to restore normal posterior cruciate ligament tension, which is associated with a visible change in the ligament shape. This method reduces the risk of an error resulting from subjectively assessing the shape of the posterior cruciate ligament. It should be also emphasized that the method combined with other ultrasound anterior cruciate ligament assessment techniques helps increase diagnostic accuracy. Methods: Ultrasonography is used as an adjunctive technique in the diagnosis of anterior cruciate ligament injury. The paper presents a sonographic technique for the assessment of suspected anterior cruciate ligament insufficiency supplemented by the use of a dynamic examination. This technique can be recommended as an additional procedure in routine ultrasound diagnostics of anterior cruciate ligament injuries. Results: Supplementing routine ultrasonography with the dynamic assessment of posterior cruciate ligament shape changes in patients with suspected anterior cruciate ligament injury reduces the risk of subjective errors and increases diagnostic accuracy. This is important especially in cases of minor anterior knee instability and bilateral anterior knee instability. Conclusions: An assessment of changes in posterior cruciate ligament using a dynamic ultrasound examination effectively complements routine sonographic diagnostic techniques for anterior cruciate ligament insufficiency.