BackgroundAt present, it is not known whether hip effusion/synovitis affects the therapeutic effect of multiple drilling core decompression (MDCD) in patients with bone marrow edema syndrome of hip (BMESH). The aims were to assess hip effusion/synovitis and its relationship with results of MDCD in patients with BMESH.MethodsThe data of undergoing arthroscopic-assisted MDCD for treatment of BMESH with hip effusion/synovitis by one surgeon were retrospectively reviewed from the associated medical records at the Affiliated Hospital of Zunyi Medical University (2016–2019). Seven patients (9 hips) participated in this study. Patients were followed up at 1, 2, 3, 6, 12 and 24 months. Data included demographics and clinical outcomes. The pre- and postoperative pain and functional outcomes were measured with the visual analogue scale (VAS), Harris Hip Score (HHS), Hip Outcome Score Activities of Daily Living subscale (HOS-ADL), International Hip Outcome Tool-12 (iHOT-12) and range of motion (ROM).ResultsSeven patients (9 hips) were followed up. Disappearance of hip pain immediately obtained at rest after surgery. All of 7 patients returned to their former activity level at postoperative 3 months, bone marrow edema had disappeared on Magnetic Resonance Imaging (MRI). The VAS, HHS, HOS-ADL, iHOT-12, and ROM at postoperative 1 month had a significant difference (P < 0.05) compared with preoperative. It was also statistically significant (P < 0.05) when compared with other time points. At the final follow-up, all patients had no limited ROM, which was symmetrical with the contralateral of hip joint. Hip effusion/synovitis were observed in 9 hips. Labral tears, cartilage fissure, and loose bodies were observed in 1 hip, respectively. Kirschner wire tracks bleeding occurred in 1 hip. No other complications occurred.ConclusionsHip effusion/synovitis could affect the clinical outcomes after MDCD in patients with BMESH. Arthroscopic procedure of hip effusion/synovitis can shorten postoperative pain relief time, disappearance time of bone marrow edema on MRI. It can simultaneously diagnose and treat other concomitant intraarticular pathologies, and be a safe operation with fewer complications.