Various types of injection therapy are available. Although some are widely accepted and used, others are considered to be more controversial. Examples of injection therapy include:

• Epidural block. Injection of an anesthetic into the space between the wall of the spinal canal and the covering of the spinal cord. It is often used to relieve pain during labor and delivery and during surgery. It may also be used to relieve back pain and neck pain. A treatment known as a spinal block is similar to the epidural block, but is injected more deeply into the fluid surrounding the spinal cord. This allows the medication to work more quickly.
  
  

• Epidural corticosteroid injections. These may be used to relieve back pain when it is believed there may be an inflammatory process involved. They may be recommended as a treatment for radiculopathy (injured nerve root) caused by conditions such as a pinched nerve, sciatica, herniated disc or spinal stenosis. A limited number of injections may help patients participate in exercise therapy and physical therapy to improve their condition.
  
  

• Facet joint injections. Anesthetics or corticosteroids are injected into the facet joints, which are located where the vertebrae of the spine connect to one another. Facet joints provide stability to the spine and help it to bend and twist. These injections will provide relief only where there are problems in the facet joints. Not all patients who suffer facet joint pathology receive relief from these injections. Some experts contend that facet joint injections may relieve back pain or neck pain, but others have found the treatment to be overused and ineffective.
  
  

• Nerve root blocks. Injection of anesthetic or corticosteroid medication into a portion of a nerve that is inflamed or compressed as it passes from the spinal column between the vertebrae. This blocks pain messages from reaching the brain, eliminating the sensation of pain.
  
  
• Viscosupplementation. A lubricant called hyaluronate is injected into a joint afflicted by osteoarthritis (OA). Hyaluronate, also called hyaluronic acid or hyaluronan, is found in synovial fluid, a gel-like substance that helps cushion many joints. The U.S. Food and Drug Administration has approved viscosupplementation as a treatment for knee OA, and its use in other osteoarthritic joints is being studied.
  
  
• Prolotherapy. A sugar solution or other irritating substance is injected into trigger points (areas where pain is thought to originate) in the fibrous tissue that covers bones. Proponents say that such injections trigger inflammation that helps promote dense, fibrous tissue to grow. According to proponents, this strengthens the attachment of tendons and ligaments that have been contributing to back pain due to their looseness. To date, studies have not corroborated these claims.
  
  
• Trigger point injections. Anesthetic is injected directly into areas of the body where pain originates. Trigger points are located by pressing on parts of the body until pain is felt. In some cases, pain is sensed in an area that is located away from the trigger point. A corticosteroid also may be included in the injection. Trigger point injections are commonly used, but recent research has cast some doubt on their effectiveness.

Some patients, such as post-surgery patients or those with severe chronic pain due to conditions such as cancer or complex regional pain syndrome, may instead be a candidate for a surgically implanted pain pump. However, whether these pumps are likely to provide any additional pain relief is controversial.