Spinal stenosis is a narrowing of the lumbar (back) or cervical (neck) spinal canal, which causes compression of the nerve roots.

                                       

Causes, incidence, and risk factors
             Spinal stenosis mainly affects middle-aged or elderly people. It may be caused by osteoarthritis or Paget's disease or by an injury that causes pressure on the nerve roots or the spinal cord itself.

Symptoms
Back pain that spreads to the legs
Difficulty or imbalance when walking
Leg pain
Neck pain
Numbness in the buttocks, thighs, or calves that is worse with standing, walking, or exercise
Pain in the buttocks, thighs, or calves that is worse with walking or exercise
Weakness of the legs
                                       

Signs and tests
Neurological examination confirms leg weakness and decreased sensation in the legs.
EMG may show neurological changes.
Spinal MRI or spinal CT scan shows spinal stenosis.
X-ray of the spine shows degenerative changes and narrowed spinal canal.


Treatment
             Generally, conservative management is encouraged. This involves the use of anti-inflammatory medications, other pain relievers, and possibly steroid injections. If the pain is persistent and does not respond to these measures, surgery is considered to relieve the pressure on the nerves.
Surgery is performed on the neck or lower back, depending on the site of the nerve compression.
Expectations (prognosis)
If the nerve roots can be successfully relieved of pressure, the symptoms will not worsen and may improve.

Complications
             Injury can occur to the legs or feet due to lack of sensation. Infections may get worse because pain related to them may not be felt. Changes caused by nerve compression may be permanent, even if the pressure is relieved.
             Spinal stenosis is narrowing of the spinal canal. This can develop as you age from drying out and shrinking of the disk spaces. (80% of the disks are made up of water) If this happens, even a minor injury can cause inflammation of the disk and put pressure on the nerve. You can feel pain anywhere along your back or leg(s) that this nerve supplies.
             Spinal stenosis is a narrowing of the lumbar or cervical spinal canal. The narrowing can cause compression on nerve roots resulting in pain or weakness of the legs. Medications or steroid injections are often administered to reduce inflammation. If the pain is persistent and does not respond to these conservative measures, surgery is considered to relieve the pressure on the nerves.
             The main nerve traveling down the leg is the sciatic nerve. Pain associated with the sciatic nerve usually originates higher along the spinal cord when nerve roots become compressed or damaged from narrowing of the vertebral column or from a slipped disk. Symptoms can include tingling, numbness, or pain, which radiates to the buttocks legs and feet.

Ref  MedlinePlus