The classical symptoms are those of pseudoclaudication, i.e. on walking, the patient experiences increasing pain, parasthesiae, weakness and sensory affliction in one or usually both legs, forcing him/her to stop. Typically, the walking distance in severe cases is only five to 10 metres, and the symptoms are usually relieved on flexing the spine. Most patients with lumbar spinal stenosis prefer using their bicycle to walking, for the same reason. The pathogenic explanation for this symptomatology is that, when walking, the spine is extended and, in this position, the spinal canal area is the least. On flexion, the square area of the spinal canal increases up to 50%. What happens in the patient with spinal stenosis on walking is that epidural venous stasis occurs, eliciting the symptoms to the legs. On flexion, the vascularisation around the nerve roots and cauda equina normalises and the symptoms subside. After this, the patient can resume walking the same distance again, thus the similarity to vascular claudication, which is caused by insufficient arterial blood supply to the leg/s.

The symptoms are therefore mainly a functional disturbance and usually occur after the age of 60 years. Due to the mechanical presentation of symptoms, analgesics usually are not very helpful, but, in some cases, low back pain due to the degeneration may be pronounced. At times, patients with spinal stenosis display low back pain only or sciatica, nerve root pain. Lumbar spinal stenosis, which is most common at the L4–L5 level, is often frequently accompanied by or elicited by a degenerative spondylolisthesis, the slipping forward of one vertebra in relation to neighbour vertebra below, at this level.

Figure 1: Spinal Stenosis at the Level of L4-L5 According to MRI Investigation, Axial Slice Through L4