The study analyzed postoperative pain in 316 patients over 40 years of age with degenerative lumbar spine disease after posterior lumbar interbody fusion (PLIF). Patients were divided into two groups according to the presence of pain: 210 without pain and 106 with pain. The results showed that age, BMI, education, length of operation, drainage time, duration of illness, time to the first ambulance and use of mannitol had no significant effect on postoperative pain (P > 0.05). Significant differences were found in gender, anxiety score (SAS), number of surgical segments, drainage volume at removal, paraspinal muscle indices (PMI, MMI), mean standing time in the first 2 weeks, and duration of straight leg raising exercises (P < 0.05). Multivariate analysis identified surgical segment (P = 0.008), drainage volume at removal (P = 0.008), MMI muscle index (P < 0.001), mean standing time (P = 0.010), and duration of straight leg raise exercise (P = 0.012) as independent risk factors. The authors recommend tailored rehabilitation focusing on improving muscle function and optimizing early exercises to reduce postoperative pain and improve treatment outcomes.