Instead of prescribing pills to control your pain, your doctor might inject medication. Injections typically don't cure pain, but they may help you through an initial period of intense pain or a flare-up of severe pain.

Injections are most effective for joint, muscle or nerve pain that's confined to a specific location. Injected medications may be an anesthetic to control the pain, a steroid to reduce inflammation or a combination of the two. In addition, a substance that improves joint mobility is also sometimes injected.

One benefit of injections is that the medication works primarily in a limited part of your body. By targeting a specific area, injections may reduce the amount of medication needed and the number and intensity of side effects.

Injections can also help in diagnosing the cause of your pain. Suppose, for example, that a small amount of anesthetic injected at a specific location relieves your pain. This may indicate that the pain is coming primarily from that joint, muscle or nerve.

In deciding whether injections may be right for you, keep in mind that you'll have to visit your doctor's office for each shot. In addition, the site of the injection and the type of medication used can limit how often you receive an injection. For instance, injected steroids may cause adverse side effects that become worse with frequent use.

Injections are seldom used by themselves to treat chronic pain. Rather, they're usually used in conjunction with a program that includes physical therapy. Injections can make such therapy more comfortable.

The types of injections can be divided into three broad categories: joint injections, soft tissue injections and nerve block injections.

When your joints become inflamed and painful, your doctor may inject medications into them to ease your discomfort. Two types of medications are used for joint injections. They are corticosteroids and hyaluronic acid.

• Corticosteroids. If arthritis has caused your joints to become inflamed, swollen and painful, your doctor may suggest injecting the affected joint with a corticosteroid. Corticosteroids mimic the effects of the hormones cortisone and hydrocortisone, which are made by the outer layer (cortex) of your adrenal glands. When prescribed in doses that exceed your natural-occurring levels, corticosteroids suppress inflammation. They are injected into one or several affected areas of your body, such as the shoulder, elbow, hip or knee. Some joint injections, such as facet or sacroiliac injections, are given in the spine.

  In the short term, corticosteroids can make you feel dramatically better. But when used for many months or years, they may become less effective and cause serious side effects. Side effects can include weakened cartilage and ligaments, easy bruising, thinning of bones, cataracts, weight gain, a round face, diabetes and high blood pressure.

  Corticosteroid injections may offer some pain relief for 4 to 6 months.

• Hyaluronic acid. Hyaluronate (Hyalgan) and hylan G-F 20 (Synvisc) are injectable drugs that are used to treat osteoarthritis of the knee. Hyaluronic acid is a substance found in normal joint fluid. Joint fluid acts as a lubricant. Hyaluronate and hylan G-F 20 help relieve pain by supplementing hyaluronic acid in the joint. These drugs may be offered if you can't get relief from exercise, physical therapy or other pain medication. Because they're injected directly into your knee, hyaluronate and hylan G-F 20 don't cause the side effects of oral pain medications.

  Hyaluronate is administered in a series of five injections — one per week — into the knee joint. A local anesthetic is injected first to ease discomfort from the hyaluronate, which is thick and must be administered with a large-gauge needle. Relief may last up to 12 months.

  Hylan G-F 20 is given in three injections. Relief may last 6 months or longer. Both drugs usually bring pain relief more slowly than do corticosteroids. Don't take Hylan G-F 20 if you're allergic to eggs.

  The effectiveness of hyaluronate injections for treating chronic knee pain associated with osteoarthritis is still being studied.

When specific parts of your body — such as a muscle or bursa — are inflamed and painful, injections can be given directly into the surrounding soft tissue.

• Trigger point or field block injections. Trigger points are areas where your muscles and surrounding fibrous (fascial) tissue are sensitive to touch. Trigger points are generally in your upper and lower back muscles, but they may occur elsewhere. Trigger point injections are used when your muscles are sensitive to touch and are the source of pain. Depending on the medication used, trigger point injections can reduce pain in your muscle, reduce inflammation or relax a muscle.

  Your doctor may inject your muscle with a preparation of local anesthetic and corticosteroid. This may reduce pain and promote increased movement. The local anesthetic initially numbs the area to reduce pain while the corticosteroid reduces inflammation. The corticosteroid begins working in 3 to 4 days and may provide long-term reduction of inflammation and pain. Sometimes an anesthetic alone is used if there is little or no inflammation and the goal is to relax the muscle for more effective stretching.

• Bursa injections. Bursa are tiny, fluid-filled sacs that lubricate and cushion pressure points between your bones and the tendons and muscles near your joints. You have more than 150 bursae in your body, and they help you move without pain. When bursae become inflamed (bursitis), movement of or pressure on the affected joint is painful. Bursitis most often affects the shoulder, elbow or hip areas. Injections of corticosteroid can be given to reduce inflammation.

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Bursitis of the shoulder Corticosteroid injections are sometimes given to reduce pain associated ... << ENLARGE

To do a nerve block, your doctor will inject an anesthetic around a nerve's fibers. This prevents pain messages that are traveling along that nerve pathway from reaching your brain. Nerve blocks are most often used to relieve pain for a short period, such as during surgery. If there is inflammation around a nerve, an injection of corticosteroid in conjunction with the nerve block may provide longer pain relief.

There are three main types of nerve blocks:

• Peripheral. For localized pain, an anesthetic is injected around a nerve that's away from the spine, such as in an ankle. The result is reduced feeling and less pain in that area.

• Spinal. For pain that affects a broader area, such as your lower back or a leg, an anesthetic is injected in or near the spinal column. An injection directly into the spinal fluid is called an intrathecal (intruh- THEE-kul) injection. This type of injection is often used during surgery on the abdomen or legs.

  If the injection isn't into the spinal fluid, it's called an epidural (ep-ih-DUR-ul) injection. Epidurals are often used to relieve the pain of childbirth and sometimes to relieve some types of back pain, such as sciatica.

• Sympathetic. Some forms of chronic pain, such as complex regional pain syndrome (CRPS), formerly called reflex sympathetic dystrophy (RSD), may result from abnormal activity of your sympathetic nervous system. Your sympathetic nerves control circulation and perspiration and are part of your autonomic nervous system. Injection of an anesthetic to block the sympathetic nerves may relieve pain.