allodynia — heightened pain in response to tactile pressure (ie. painful to touch)

disc —  the structure located between each vertebrae in the spine (except between the 1st and 2nd vertebrae in the neck). A disc has 2 components. The outer part of the disc is called the annulus fibrosus and is composed of layers of fibrous tissue. The inner part of the disc is called the nucleus pulposus and is composed of soft, spongy material and water.

ankylosing spondylitis — this is a chronic inflammatory disease of unknown cause that affects the spine and sacroiliac joints (as well as other joints) leading to progressive fusion. It affects mostly men under 30 years of age.

disc herniation — displacement or extrusion of a piece of nucleus pulposus from the centre of the disc to a location outside of the annulus of the disc.

failed back surgery — referring to people who have undergone an operation on their spine, usually for the relief of back and/or leg pain but who have not improved following the surgery. This occurs in 5 – 25% of all spine operations.

fibromyalgia — a chronic pain condition characterized by widespread pain and tenderness involving muscles and soft tissue. It is thought to be precipitated by stress. Other symptoms of this condition (besides pain) include fatigue, sleep disturbance and depression.

lumbar spinal stenosis — a narrowing of the spinal canal which is the area in the spine that contains the nerve roots.

sacroiliac joint — the joint between the sacrum and ileum which are the bones that form the pelvis.

sacroiliitis inflammation of the sacroiliac joint(s). It can be an early finding in patients with ankylosing spondylitis.

sciatica — pain radiating down the leg in the distribution of a component of the sciatic nerve. It is usually due to compression of a nerve root in the spine, not compression of the sciatic nerve itself.

spinal stenosis — a narrowing of the spinal canal which is the space that contains the spinal cord (cervical and thoracic spine) or nerve roots (lumbar spine).

spondylosis — non-specific degenerative changes of the spine. This can involve the disc, facet joints and ligaments.

spondylolysis — a defect or break in the bone known as the pars interarticularis which is part of the posterior bony arch.

spondylolisthesis — an anterior subluxation of one vertebral body on another.