Injection therapy involves using a needle and syringe to relieve pain by injecting medication into a patient's joints, soft tissues or other areas. It typically is used only when less invasive forms of treatment fail to relieve symptoms.

Types of injection therapy include:

• Facet joint injections. Anesthetics or corticosteroids are injected into the facet joints, which are located between the vertebrae.
  
  
• Nerve root blocks. Anesthetics or corticosteroids are injected into a portion of a nerve that is inflamed or compressed.
  
  
• Viscosupplementation. A lubricant called hyaluronate is injected into a joint afflicted by osteoarthritis.
  
  
• Prolotherapy. A sugar solution or other irritating substance is injected into trigger points (areas where pain is felt) in the fibrous tissue that covers bones. This is believed to trigger inflammation, which causes fibrous tissue growth that can strengthen the area.
  
  
• Trigger point injections. Anesthetic is injected directly into areas of the body where pain is present.

Examples of conditions that may be treated with injection therapy include carpal tunnel syndrome, sciatica, arthritis, bursitis, tendinitis and tennis elbow.

In most cases, injection therapy is an outpatient procedure using a local anesthetic. A fluoroscopic x-ray may be performed to help the physician guide the needle to the right spot. Patients often are able to resume their daily activities within a brief period of time following the procedure.

Injection therapy is usually a safe procedure. However, side effects sometimes occur, such pain, bleeding, infection or nerve damage.

Controversy remains over the effectiveness of injection therapy. Though some experts recommend them, studies have not conclusively shown injection therapy to be effective in treating certain types of pain.

Injection therapy involves using a needle and syringe to inject anesthetic, corticosteroid, opioid or other medication into a person's body to relieve pain that does not respond to other forms of treatment. It is usually more effective in treating acute pain but may also be used to treat chronic pain.

During these treatments, medication is injected into the soft tissues, joints and other areas in and around the source of a patient's pain. Exactly how these injections exert their analgesics effects remains unclear.

The pain-relieving properties of injection therapy function in different ways depending on the site of the injection. In some cases, the injection is made into the epidural space, the area between the spinal sac and inside of the spinal canal (but not in the spinal fluid). The injected medication moves up and down the spine and coats the nerve roots and the outside lining of the spine’s facet joints (adjacent vertebrae) near the injection area. In other cases, the injection may be made directly into the facet joint, which may decrease inflammation in the joint.

Depending on the source of a patient's pain, injections also may be made into various joints. For example, injection therapy into the joint that connects the bottom of the spine with the hip (sacroiliac joint) may help to relieve back pain. Injection therapy also may be used to help relieve pain associated with arthritis, particularly in a patient's knees. Medications such as hyaluronate may act as a lubricant to the joint, which usually decreases pain. In other cases, the injection is made into trigger points (areas that are tender to pressure).

A combination of anesthetic (to relieve pain) and corticosteroid (to reduce inflammation) is used in most injection therapy treatments. In some cases, an opioid (narcotic) medication also may be used to enhance pain relief.

Controversy remains over the effectiveness of some forms of injection therapy. For example, studies have not shown injection therapy to be effective in treating many types of back or neck pain. The most recent literature indicates that many forms of blocks including epidural steroid injections have not been found to have any long- term benefits.

In addition, certain patients are not good candidates for injection therapy. This includes people prone to excessive bleeding and those taking anticoagulants (medications that decrease the clotting ability of blood). In addition, some forms of injection therapy, specifically the use of corticosteroids, are not recommended for patients whose pain results from infection or some forms of cancer. Corticosteroids can reduce immune system response, so patients who are fighting any type of serious infection should not undergo treatment with this type of medication. In addition, spinal injections increase the risk of spreading the infection into the spine, which can lead to meningitis.

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.

Many conditions may be treated with injection therapy, including:

• Pain in and around the spine (e.g., back, neck, hip). This may be due to a number of causes, including skeletal disorders, disc disease or painful knots of muscle. However, in more than 80 percent of cases of chronic back pain, there is no clearly identifiable etiology (cause).
  
  
• Bursitis. Inflammation of a bursa, a fluid-filled pad located throughout the body that lubricates areas where tendons and muscles pass over bony projections. It can occur in a number of areas of the body, including the shoulder, elbow, hip, knee and ankle.
  
  
• Carpal tunnel syndrome. Wrist condition resulting in numbness, weakness and other symptoms in the hand and fingers. Carpal tunnel syndrome is due to compression of the median nerve in the wrist, according to the National Institutes of Health. However, many patients have surgery to relieve the compression but don't have a reduction in symptoms, and there are people who have identifiable compression of the nerve without any symptoms.

• Neuralgia. Pain resulting from injury to the nerves. The area of the body affected depends on the specific nerve pathway affected.  Types of neuralgia include postherpetic neuralgia, which results from shingles and usually affects the trunk or the face and scalp, and cranial neuralgias such as trigeminal neuralgia. Patients may experience sensations that include pins and needles, shock-like episodes, sharp stabbing pain or a constant burning pain.
  
  
• Osteoarthritis. Arthritis caused by wear to joints. Common areas affected include the hands, hips, knees, neck and lower back.

• Rheumatoid arthritis. Inflammatory disorder in which the immune system attacks the body.
  
  
• Sciatica. Pain that radiates along the longest nerve in the body (the sciatic nerve). This nerve runs from the pelvis through the buttocks and hip area and down the back of each leg. Pain is usually the result of pressure on the nerve.
  
  
• Shingles. Condition that affects nerves in the skin, causing a painful rash in people who previously have had chickenpox or the chickenpox vaccine.
  
  
• Tendinitis. Inflammation or irritation of a tendon due to overuse. It commonly affects the shoulders, knees, elbows and hips.
  
  
• Tennis elbow (lateral epicondylitis). Inflammation or pain on the outside of the upper arm near the elbow.

• Golfer elbow (medial epicondylitis). Inflammation or pain along the inner elbow.
  
  
• Cancer pain. Cancer patients may receive opioid injections for pain. Pain caused by pancreatic cancer may be treated with celiac plexus blocks.
  
  
• Cervical dystonia. A painful nerve disorder that causes severe contractions of neck and shoulder muscles. The U.S. Food and Drug Administration (FDA) has approved injections of neurotoxins called botulinum toxin type A (Botox) and botulinum toxin type B (Myobloc) to treat cervical dystonia.

The FDA has also approved Botox injections to treat two eye muscle disorders (blepharospasm and strabismus) and severe underarm sweating (primary axillary hyperhidrosis). Scientists are studying Botox as a potential treatment for many other conditions, including migraines, osteoarthritis, writer's cramp, back pain and prostate enlargement (benign prostatic hyperplasia).

Injection therapy usually is not recommended until a patient has undergone more conservative treatments designed to relieve symptoms of discomfort. This may include rest, anti-inflammatory and other analgesic medications, physical therapy and exercise to strengthen the muscles and increase flexibility. Injection therapy will be considered only if less invasive treatment methods fail to relieve a patient’s symptoms.

In preparation for injection therapy, imaging tests such as a CAT scan (computed axial tomography) or MRI (magnetic resonance imaging) may be performed to look at the area causing pain.

Prior to the procedure, patients may be asked to follow a number of preparatory steps. These may include avoiding the use of anti-inflammatory medications for a period of time. Depending on the type of injection, the patient may be told not to eat for a certain number of hours prior to undergoing the procedure. Some patients may be advised not to use anticoagulants (medications that reduce the clotting ability of blood), as these can increase the risk of bleeding during the procedure.

In most cases, injection therapy is an outpatient procedure, performed in a physician's office or in a hospital, using a local anesthetic.

Depending on the area to be treated, patients may lie on an x-ray table or may recline or sit in a manner that allows the muscles to be relaxed. A fluoroscopic x-ray may be used to help the physician guide the needle to the right spot. The injection site is cleaned and sterilized and the local anesthetic is administered to numb the skin. A contrast medium is injected into the injection area to highlight the region on an x-ray. Using the x-ray, the physician can be sure of guiding the needle into the proper part of the body.

Before administering the therapeutic injection, the physician may administer a diagnostic injection. A small amount of an anesthetic medication is injected into the area suspected of causing the pain to see how the patient's symptoms react to the injection. If the patient reports a reduction in pain after this limited injection, it likely indicates that the physician has located the proper injection site. A therapeutic injection of anesthetic and analgesic medications will then follow.

This process may be repeated several times if more than one area of the body requires treatment. Following the procedure, patients may be asked to perform a task that normally causes them to feel pain in the area that has just been treated.

Once the anesthetic wears off, patients may experience a return of their pain until the medication begins to work. This can take anywhere from a few days to a week or longer. Most patients are able to return to their normal activities almost immediately following the procedure.

Patients who have injections such as epidural blocks or viscosupplementation may be required to return for follow-up injections over a period of a few weeks.

Injection therapy is usually considered as only one step toward long-term pain management. Patients typically are urged to participate in a follow-up program of physical therapy, exercise, weight loss and other steps that can increase the odds of managing the pain permanently.

Injection therapy is usually a safe procedure, and it sometimes provides pain relief that can last for weeks or even months at a time. While patients are enjoying this pain-free period, they may be better able to complete physical therapy, exercise therapy and other rehabilitation that can help them avoid future bouts of pain.

However, side effects sometimes occur with these treatments. This may include pain, bleeding or infection at the injection site. Infection typically is indicated by fever in addition to redness, fluid or odor at the injection site. Patients who experience these symptoms are urged to contact their physician.

After injection therapy to areas around the spine, some patients may experience a spinal headache (also known as a post-dural puncture headache). This can result from spinal fluid leakage from the epidural space, which decreases fluid pressure around the spinal cord and brain, causing a headache. Movement (e.g., getting up and walking around) too soon after the procedure is associated with the onset of spinal headaches. Spinal headaches may occur days after the injection, and bed rest for a day or two following the procedure may be recommended.

The severity of spinal headaches may lessen when a patient lies down. Drinking caffeinated beverages, which constricts blood vessels and increases spinal fluid pressure, may also help relieve these headaches. In some cases, patients may need to receive intravenous fluids to increase spinal fluid pressure and relieve the headache. A blood patch, in which the patient's own blood is injected to seal the leak, may also be used to relieve a spinal headache.

There is a small risk of damage to spinal nerves that could result in neurological complications. Some patients may have bladder-control problems for an hour or two following the procedure, as the nerves of the bowel and bladder may be temporarily paralyzed following certain types of injection therapy (e.g., epidural block).

Other side effects of injection therapy may include elevated blood pressure and nausea.

Preparing questions in advance can help patients have more meaningful discussions with healthcare professionals regarding their condition or test. Patients may wish to ask their doctor the following questions about injection therapy:

1. What are your feelings about the effectiveness of injection therapies?
   
   
2. What type of injection therapy might help me?
   
   
3. How should I prepare for the procedure?
   
   
4. Should I have someone drive me to and from the procedure?
   
   
5. How long will the procedure take?
   
   
6. What are the risks associated with the procedure?
   
   
7. Will there be any limits on my daily activity following the injection?
   
   
8. Will I require follow-up injections?
   
   
9. What other types of treatments might help prevent my pain from returning?
   
   
10. What are my options if injection therapy does not relieve my symptoms?