Degenerative disc disease is a process of intervertebral disc ageing characterized by wear and tear changes. These changes can be accelerated by injury, lifestyle and type of occupation. Disc herniation occurs when the core of the disc extends beyond disc boundary. If we imagine your disc as a pillow, than putting pressure on one side causes bulging on the other hence disc bulge. When the core of the pillow rips the cover and actually comes through that is what we think of as disc herniation. When part of the pillow core completely separates from the disc that is what we call free disc fragment. Disc bulge, herniation or disc fragment can exert pressure on nerve roots and cause irritation, swelling and inflammation. This can cause pain, weakness and sensory changes in the part of the body supplied by the affected nerve root and that is what we refer to as radiculopathy. In severe cases it can also cause bowel and bladder symptoms. Any pain shooting down the leg is usually referred to as sciatica however it is a very non-specific term.
Spinal stenosis refers to narrowing of the spinal canal. This may affect the Cervical (neck) or Lumbar spine. The spinal canal is the main corridor for spinal the spinal cord and spinal nerves. Narrowing of the spinal canal is usually caused by overgrown bone and soft tissue of the spine. Prolonged compression of nerve tissue causes insufficient blood supply and also direct damage which manifests as pain, weakness and sensory changes. In cases of lumbar spinal stenosis, it usually causes general pain and fatique in legs when walking or standing. This is called pseudoclaudication. Stopping, bending over or sitting alleviates pain. Pain can be predominant in one leg and can have a sharp pain component in cases of nerve roots being trapped. In cases of cervical (neck) stenosis affecting cervical nerve roots it can cause pain, weakness and sensory changes in the arms and hands. More centrally placed stenosis compresses the cervical spinal cord and this can also affect your legs in terms of unspecific weakness, instability and difficulty with coordination. This is then called myelopathy.
Spondylolisthesis is a condition when vertebral bodies do not maintain proper alignment and there is a visible slip on imaging. In many cases it causes no symptoms but over time it can produce back pain, leg pain, numbness, weakness or combination thereof. It is often combined with spinal stenosis.