The dissertation is focused on lumbar spinal stenosis (LSS), because it is a serious desease, that primary affects elderly patients and which often leads to disability. Because the pathophysiology or feasible prophylaxy is not yet fully understood, the first part of the thesis is devoted to the ligamentum flavum (LF), whose changes (hypertrophy and degeneration) are one of the main factors leading to LSS. We focused in this experimental part on changes in the LF properties that could cause its degeneration and hypertrophy - changes in vascularization (investigated as vascular density - Lv), the presence of inflammatory changes and the occurrence of chondroid metaplasia, and then to clarify changes in the LF mechanical properties (stiffness). Vascular density analysis of degenerated and healthy human LF combined with measurement of micromechanical properties was performed. It was found that Lv changes were not dependent on the degree of LSS but were age dependent, that is, LF vascular density declines up until 50 years of age and thereafter changes very little. A significant increased incidence of chondroid metaplasia and clear signs of inflammation in LSS patients were found out. LF samples from LSS patients showed significantly lower stiffness in comparison to samples of healthy patients. The...