This document examines the reliability of using ultrasound imaging to measure the depth and translation of lumbar vertebral bodies. It finds that intra-rater and inter-rater reliability for measuring depth is good, with intraclass correlation coefficients above 0.9. However, measuring sagittal translation between flexion and extension has higher error. While ultrasound shows potential for identifying spondylolisthesis, comparisons to gold standards and controlling for transducer pressure are needed.