The special shape deformity associated with severe lower lumbar spondylolisthesis deserves special mention. Here, x-rays show local kyphosis between the anteriorly and inferiorly sagged L5 vertebra and the sacral bone, whereby the sacrum is often in an abnormal vertical position, whilst above L5 compensatory exaggerated lordosis has developed, which is also visible externally. The legs are flexed in the hips and it is impossible for the patient to stoop forward and difficult to lift the legs whilst they are stretched due to tight hamstrings. This is a reflectory shortening of the hamstrings due to the profound sliding of L5 and the resultant traction on the local lower lumbar nerve roots. In cases of severe spondylolisthesis, irregular alignment is nearly always palpable at the location of the shift.