STUDY DESIGN: This is a retrospective study. OBJECTIVES: We wanted to verify the value of radiography and gait analysis to analyze the changes of the pelvic tilt before and after gait in the patients with LDK. Summary of Literature Review: Patients with lumbar degenerative kyphosis show dynamic changes that are closely associated with the motion of pelvis. MATERIALS AND METHODS: We analyzed 18 lumbar degenerative kyphosis patients who didn't have multiple vertebral compressio fractures, a past history of spinal surgery or surgery for degenerative arthritis of the knee or hip, and obesity which causes marker errors on the gait analysis. Pelvic tilt was statistically evaluated by utilizing radiographs and dynamically utilizing the gait analysis. The linear parameters of the gait cycle and the kinematic data were obtained from the gait analysis. RESULTS: The LDK patients'mean walking velocity was 80.7 cm/s, and it was largely decreased to 65% of the normal value. The cause of the decreased walking velocity was a decrease of stride length, and not a decrease of cadence. The mean static pelvic tilt in the gait analysis was -1.3+/-8.0degrees , and there were 8 cases of anterior tilt and 10 cases of posterior tilt. The mean pelvic tilt during gait was 12.5+/-8.2degrees , and there were 17 cases of anterior tilt and 1 case of posterior tilt. It was statistically significant difference (p<0.05) between the mean static pelvic tilt in gait analysis and the mean pelvic tilt during gait and the Pearson's correlation coefficient was -0.88. CONCLUSIONS: Though there was no statistical significance, we observed anterior pelvic rotation after gait on the radiographs. As fatigue of the pelvic extensor muscles increases during gait, anterior pelvis tilt increases with statistical significance on the gait analysis. Therefore, we feel gait analysis is useful for evaluating the dynamic change of the pelvic tilt in patients with LDK.