Objective:To compare the clinical effects of hip arthroplasty through direct anterior approach (DAA) in lateral decubitus in the treatment of hip osteoarthritis caused by Kaschin-Beck disease and congenital acetabular dysplasia.Methods:The prospective study method was used to select the patients who needed hip arthroplasty in the Fourth Department of Orthopedics, the Second Affiliated Hospital of Harbin Medical University from January 2015 to December 2019. All of them were operated with lateral decubitus DAA. According to the inclusion criteria, they were divided into Kacshin-Beck disease hip osteoarthritis group (group A) and congenital acetabular dysplasia hip osteoarthritis group (group B). Hip Harris score, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, visual analogue scale (VAS) score were conducted, and hip abduction angle and flexion angle were measured before surgery, 3, 14 days and 1, 3, and 12 months after surgery.Results:Nineteen and twenty-two patients were included in group A and group B, respectively. All patients successfully completed the surgery. There was no significant difference in Harris score between the two groups before surgery, 3, 14 days, and 1, 12 months after surgery ( P > 0.05). There were no significant differences in WOMAC score, VAS score, hip abduction angle and hip flexion angle between the two groups before surgery and each time point after surgery ( P > 0.05). In the same group, there were significant differences in Harris score, WOMAC score, VAS score, hip abduction angle and hip flexion angle at different time points ( P < 0.001). All postoperative indicators were significantly improved compared with those before surgery. Conclusions:There is no significant difference in the clinical effects of hip arthroplasty through lateral decubitus DAA in the treatment of hip osteoarthritis caused by Kaschin-Beck disease and congenital acetabular dysplasia. This surgical method has good therapeutic effect on both types of hip osteoarthritis.