Abstract: Objective To compare the differences  of coronal lower limb  parameters between the patients with osteoarthritis secondary to developmental dysplasia of the hip（DDH） and normal young adults on the coronal plane.Methods The radiographic data of 62 patients with osteoarthritis secondary to DDH were retrospectively reviewed.The DDH group was divided into two subgroups including unilateral DDH group（46 cases）and bilateral DDH group（32 sides of 16 cases）.62 healthy individuals were recruited to form a control group.Full leg length standing anterior-posterior radiographs was collected and 7 parameters were measured in the coronal plane，including Hip-Knee-Ankle angle（HKA），Neck-shaft Angle（NSA），Mechanical Lateral Distal Femoral Angle（mLDFA），Anatomical Lateral Distal Femoral Angle（aLDFA），Medial Proximal Tibia Angle（MPTA），Femoral Bowing Angle（FBA），Joint Line Convergence Angle（JLCA）.Results The HKA angle（-1.78±3.4）° in DDH group may be more prone to presenting varus alignment than those in the control group（1.78±2.50）°（P＜0.05）.The incidence of valgus alignment in DDH group（50%）was significantly higher than that in control group（2%）（P＜0.05）.The mLDFA in DDH group（85.12±3.81）° was significantly smaller than that in control group（87.49±3.64）°（P＜0.05）.The aLDFA in DDH group（79.02±3.91）° was significantly smaller than that in the control group（83.34±2.59）°（P＜0.05）.The mMPTA and JLCA of DDH group was （86.34±3.24）°and（1.07±1.91）°，respectively，whilce in control group was（86.51±3.02）°and （0.95±1.64）°，respectively（both P>0.05）.The NSA and FBA of DDH group was （146.95±12.61）°and（5.30±4.09）°，respectively，whilce in control group was（131.40±5.51）°and （2.96±2.18）°，respectively（both P＜0.05）.Conclusion The patients with osteoarthritis secondary to DDH may be more apt to presenting varus alignment deformity，which may be related to morphological changes of distal femur and proximal femur，instead of intra-articular factors and anatomical changes of proximal tibia.

Key words: hip dysplasia, morphological analysis, lower limbs, knee