Imai N, et al. - A total of 73 women (146 legs) with bilateral hip dysplasia and 45 healthy women (90 legs) without lumbago, knee symptoms, or osteoarthritic findings of the knee or spine on plain radiographs were recruited in a study by the researchers in order to evaluate the morphological variations in the knee joint related to knee rotation angle in individuals with hip dysplasia, which could, in turn, describe the anatomy of the knee in patients with hip dysplasia and help in planning knee surgery. In both the normal and developmental dysplasia of the hip groups, the condylar twist angle and the length of the posterior part of the lateral femoral condyle were statistically positively associated with the knee rotation angle. In the developmental dysplasia of the hip group, the knee rotation angle had no statistical association with femoral neck anteversion yet in the normal group, it had a statistical relationship with femoral neck anteversion. In conclusion, hip dysplasia influenced knee joint morphology. In both the normal and developmental dysplasia of the hip groups, the length of the posterior part of the lateral femoral condyle was significantly positively related with knee rotation angle which symbolized that a greater posterolateral dimension was correlated with a greater knee rotation angle. Moreover, in total knee arthroplasty, these morphological knee joint variations in individuals with hip dysplasia may aid in concluding the alignment of prostheses.