AbstractParaspinal (erector spinae and multifidus) and psoas muscles contribute to spinal stability, but no study has yet examined the relationship between muscle mass and recurrent lumbar disc herniation (rLDH). The purpose of this study was to investigate the effect of psoas and paraspinal muscle mass on recurrent Lumbar disc herniation (LDH). This retrospective study included 49 patients with LDH (22 men, 27 women; mean age: 59.9 years; range 32-80) who underwent discectomy and partial laminectomy without fusion and underwent both pre- and postoperative magnetic resonance imaging. The presence of rLDH was determined using medical records and postoperative magnetic resonance imagings. Patients were divided into an rLDH group (26 patients) and a without-rLDH group (23 patients). Clinical characteristics, segmental motion, and paraspinal and psoas muscle mass were compared between the groups. Using ImageJ software, the cross-sectional area (CSA), lean muscle mass (LMM), and skeletal muscle index (SMI) were measured on T2 axial preoperative magnetic resonance images at L2-L3, L3-L4, and L4-L5 disc levels to represent muscle mass. Univariate and multivariate logistic regression analyses were performed. In the rLDH group, patients were younger (52.6 years vs 68.2 years; P = .001), segmental instability was more common (50.0% vs 4.3%; P = .001), and the CSA, LMM, CSASMI, and LMMSMI of psoas muscles were larger (5851.59 mm2 vs 4264.93 mm2, 5456.59 mm2 vs 4044.77 mm2, 18.77 cm2/m2 vs 13.86 cm2/m2, and 17.52 cm2/m2 vs 12.98 cm2/m2; P < .01 for all 4 variables). On multivariate logistic regression, age and segmental instability were independent risk factors for rLDH (odds ratio 0.886 and 18.527; P = .01 and P = .02, respectively). In middle-aged and elderly patients with lumbar disc herniation, relatively younger age, segmental instability, and greater psoas muscle mass may be risk factors for recurrence.