Abstract:[Objective] To search the relationship between the resection extent of the lumbar facet joint (FJ) and the postoperative clini-cal outcome and the lumbar stability after endoscopic lumbar decompression. [Methods] A retrospective research was conducted on 87 pa-tients who received endoscopic decompression for lumbar spinal stenosis (LSS) in our hospital from January 2019 to October 2023. Basedon the FJ resection extent measured by CT after operation, the patients were divided into four groups, including 22 patients in the minimalgroup with 0~25% FJ resected, 22 patients in the small group with 26%~50% FJ resected, 21 cases in the medium group with 51%~75%FJ resected, and 22 patients in the vast group with 76%~100% FJ resected. The perioperative, follow-up and imaging data of the 4 groupswere compared. [Results] There were no significant differences in operation time, incision length, intraoperative blood loss, intraoperativefluoroscopy times, postoperative walking time, hospital stay and incidence of adverse events among the 4 groups (P＞0.05). All patients inthe 4 groups were followed up for more than 12 months, and the minimal and small groups resumed full weight-bearing activities signifi-cantly earlier than the medium and vast groups [(87.8±4.3) days vs (88.6±8.0) days vs (94.6±7.3) days vs (94.3±8.8) days, P=0.002]. As time went on, the VAS scores for low back pain and leg pain, as well as ODI and JOA scores were significantly improved in all of the 4 groups(P＜0.05). One month after surgery, the minimal and small groups proved significantly superior to the medium and vast groups in terms oflow back pain VAS [(1.9±0.8) vs (2.0±0.5) vs (2.8±0.7) vs (2.9±0.8), P＜0.001], ODI [(27.4±3.5) vs (28.3±1.8) vs (30.1±3.2) vs (30.6±3.2), P=0.002], and JOA score [(25.1±1.3) vs (25.1±1.1) vs (23.1±1.6) vs (23.3±1.6), P＜0.001]. As for imaging, the spinal canal area was significant-ly increased in all the 4 groups after surgery compared with that before surgery (P＜0.05), but the lumbar angular displacement was only sig-nificantly increased in the medium and vast groups (P＜0.05). At the time of the last follow-up, the minimal group and small group was supe-rior to the medium and vast group regarding the lumbar angular displacement [(7.6±2.2)° vs (9.4±3.4)° vs (10.4 ±2.2)° vs (10.6±2.3)°, P＜0.001]. [Conclusion] The greater FJ resection extent under endoscope for LSS, the greater the angular displacement on the image 1 year af-ter surgery. The FJ resection extent is somewhat related to the short-term postoperative symptoms of lumbar pain and the recovery of lum-bar function. Endoscopic decompression should not involve more than 50% of FJ.