The relevance of knee injuries in accidents involving passenger cars and pedestrians or cyclists is not clear. Past studies using different research methods and data sources came to different conclusions. This study aims to analyse the frequency of knee injuries based on a new dataset from insurance claims data in Switzerland. The study sample contains 340 real-world accidents, each representing an impact between one passenger car and one pedestrian or cyclist. Injury descriptions, accident details and vehicle information were extracted from medical and police reports and insurance data. In 123 pedestrian and 217 cyclist accidents, knee ligament injuries were sustained in eight accidents, which represents 16% of the accidents with injuries of the lower extremities (excluding superficial injuries). In total, 37 knee injuries were reported, of which 13 were knee ligament ruptures and 10 were bone fractures in the knee area. It was observed that ligament injuries were mostly diagnosed three or more days after the injury, which might explain the different prevalence of ligament injuries in different data sources. Based on this analysis, knee ligament ruptures are relevant for the assessment of modern vehicles and should therefore be considered in virtual testing procedures addressing the protection of pedestrians and cyclists.