Introduction: Much of lower back pain (LBP) is thought to be mechanical in origin and lower limb amputees have an increased prevalence. There is also evidence that a large proportion of them also have altered spinal posture and it is commonly thought that the movement between the vertebrae (kinematics) may be affected. The current study was designed to explore the kinematics of the lumbar spine segments in trans-tibial amputees and compare it to a similar population with intact lower limbs using quantitative fluoroscopy (QF). The study also investigated possible relationships between lumbar spine stability and the motion between the prosthetic socket and residual limb. It is hoped that these investigations will improve understanding of the importance of limb-socket fit to the functional integrity of the lumbar spine in lower limb amputees. Methods: A literature review and three preliminary QF studies were carried out; one to the determine the best plane of motion and orientation of participants during QF imaging of the spine, a second to inform the optimal imaging protocol for the limb-socket interface and the third to validate a QF measurement of inter-vertebral stability. This phase determined the measurement parameters and investigative protocols. Given the complexity of the technique, 12 male below knee amputees and 12 healthy male controls of similar age and body mass index were recruited and received passive recumbent coronal QF imaging of their lumbar spines. This was followed immediately by anterior-posterior QF imaging of their limb-socket interfaces during three different forms of simulated gait. Differences between amputee and control spine kinematics and relationships between limb-socket motion and inter-vertebral kinematics in amputees were investigated. Results: Passive recumbent coronal plane QF appears to be a valid method for measuring inter-vertebral stability. Although there were no systematic differences between the magnitude of inter-vertebral kinematics variables of amputees and controls, there was a trend towards greater variability in both inter-vertebral range and symmetry of motion in amputees and a significantly higher proportion of correlations in attainment rate between levels among amputees than controls (2-sided p < 0.04). There was also a substantial, statistically significant inverse linear relationship between passive inter-vertebral motion symmetry and limb-socket telescoping in amputees. Conclusions: This thesis provides evidence that the kinematics of the lumbar spine may be affected by lower limb amputation – particularly in respect of socket fit. The importance of consistency and symmetry of restraint by the intrinsic spinal holding elements in trans-tibial amputees has been highlighted. An indication of a relationship between limb socket telescoping and spine kinematics was identified, suggesting the need for replication of this part of the study in a larger amputee population. The variables of interest and the basis for this have been identified. Finally, inter-vertebral motion pattern variation has been associated with chronic low back pain in the literature. It was discovered that there was more interdependence in passive inter-vertebral motion between and across levels in below knee amputees than controls in terms of laxity, but not range of motion. The apparent relationship between this and socket fit in amputees suggests a possible mechanism and diagnostic subgroup in this population.