Abstract:[Objective] To investigate the clinical outcomes of hip arthroscopy for femoroacetabular impingement (FAI) accompanied borderline developmental dysplasia of the hip (bDDH) . [Methods] A retrospective study was conducted on 232 patients who underwent hip arthroscopy for FAI in our hospital from September 2017 to December 2019. Of them, a total of 22 patients who were under 50 years old, and met the criteria for diagnosis of bDDH, with lateral center edge angle (LCEA) between 18° and 25° were enrolled into this study. All the 22 patients underwent arthroscopic labrum repair, femoroplasty and capsule tightened suture. [Results] As arthroscopic findings, all the 22 patients had labral tear in different extents and cam-like malformations at the femoral head and neck junction, which were treated accordingly. All the 22 patients were successfully operated on without any important vascular or nerve injury. The follow-up period lasted for 15-39 months, with a mean of (22.29±6.78) months. The VAS scores significantly decreased (P<0.05) , while the mHSS and iHOT-12 scores significantly increased at the latest follow up compared with those preoperatively (P<0.05) . At the latest follow-up, the mHHS score in the male (13/22) were significantly higher than that in the female (9/22) (P<0.05) . Radiographically, the LCEA and α angle decreased significantly (P<0.05) , while T?nnis angle and FHNO significantly increased compared with those preoperatively (P<0.05) . The T?nnis os- teoarthritis classification remained unchanged in all patients at the last follow-up. [Conclusion] The proportion of FAI accompanied with bDDH is 9.48% in all FAI patients. Arthroscopic labrum repair, femoroplasty combined with capsular tightened suture does achieve satis- factory short-term outcomes for this condition.