ObjectiveTo investigate the effectiveness of arthroscopic iliopsoas tendon tenotomy at the labral level for iliopsoas cyst complicated with internal snapping hip. Methods A retrospective analysis was conducted on the clinical data of 9 patients diagnosed with iliopsoas cyst and internal snapping hip admitted between April 2021 and June 2023. The cohort consisted of 3 males and 6 females, aged 23-58 years with a mean age of 40.7 years. The disease duration ranged from 11 to 24 months, with an average of 16.7 months. Preoperative MRI showed that 9 cases were complicated with glenoid labrum tear, iliopsoas muscle cyst extended from the glenoid level to the proximal end of the lesser trochanter, and compressed the femoral artery and vein. The iliopsoas tendons were cut at the level of glenoid labrum under arthroscopy. Pincer plasty (7 cases), glenoid labrum repair (6 cases), or glenoid labrum debridement (3 cases) was performed according to the lesions during operation, and the cyst drainage and cyst wall debridement were completed. Imaging examinations were performed before operation and at 2 days after operation to measure the lateral central-edge angle (LCE), α angle, off-set value, and the distance from femoral artery and vein to acetabular rim. The modified Harris Hip Score (mHHS), the 12-item International Hip Outcome Tool (iHOT-12), and the visual analogue scale (VAS) score were used to assess hip function before operation and at last follow-up, and the hip flexion and external rotation muscle strength in supine position were compared. ResultsAll patients completed the surgery successfully. The operation time ranged from 50 to 92 minutes (mean, 67.3 minutes), and intraoperative blood loss was 10-25 mL (mean, 18.9 mL). Pain and snapping symptoms resolved immediately after operation, and no complications such as femoral nerve injury, femoral arteriovenous injury, or incision infection occurred. Imaging examinations at 2 days postoperatively showed that the α angle, LCE, and the distances from the femoral artery and vein to the acetabular rim significantly decreased when compared with preoperative values, while the offset value significantly increased, with all differences significant (P<0.05). All the 9 patients were followed up 22-45 months (mean, 35.0 months). During the follow-up, no recurrence of hip snapping was observed; hip pain, daily living ability and activity function were markedly improved. At last follow-up, the mHHS score, iHOT-12 score, VAS score, as well as hip external rotation muscle strength were all significantly improved when compared with preoperative values (P<0.05), but there was no significant difference in hip flexion strength between before and after operation (P>0.05). ConclusionArthroscopic iliopsoas tendon tenotomy at labral level complicated with internal snapping hip can effectively relieve the pain and snapping symptoms of iliopsoas cyst combined with medial snapping hip, and promote the recovery of hip function, which is a safe and effective minimally invasive operation.