The mechanical behaviour of anulus fibrosus is dependent on collagen fibers and influences the prolapse disposition. The aim of study was the comparison of constitutional mechanical tissue properties between a group of patients with disk herniation and normal. A computerized finger hyperextensiometer was developed which was able to analyse the viscoelastic tissue properties. In the disc herniation group the hyperextension angle of the metacarpophalangeal joint was smaller (p < 0.001), the relative integral area of the force/angle regression was larger (p < 0.001), the relative area under the secant of the curve (p < 0.01) and the recover value were smaller (p < 0.01). The results suggest that a anulus fibrosus with constitutional reduced extensibility, stress absorption capacity and recovery is disposed to herniation.