Why would a doctor perform a joint aspiration or joint injection?
Your doctor may perform these procedures if you have pain, swelling, or tenderness in a joint that just won’t go away.
What causes painful joints?
Inflammation (redness and swelling) is a normal reaction in the
human body. For example, when a foreign substance (such as bacteria or a virus)
enters the body, your body’s immune system goes into action. Led by the white
blood cells, your immune system releases chemicals to attack the unwanted substance.
The same thing may happen when a joint is overworked or injured.
Your immune system steps in to help ease the pain of the joint. Usually, this
process is well-controlled: some slight, temporary inflammation occurs in the
joint, and then clears up.
But in some cases, the white blood cells, and the chemicals they
release to protect you, can damage sensitive tissues. This leads to more
inflammation and causes pain and tenderness that either won’t go away, or seems
to go away but keeps coming back.
This pain and tenderness is often caused by a build-up of fluid
in the joint. This fluid is made up of the white blood cells and the chemicals
they release, along with other fluids such as red blood cells and lubricants
that, in normal amounts, help the joints work smoothly.
What is a joint aspiration?
In a joint aspiration, your doctor inserts a thin needle
into the joint and removes some of this excess joint fluid. He or she may then
send it to a laboratory for analysis. The lab test can be used to test for the
presence of infection, numbers of white and red blood cells, as well as
substances such as protein, glucose, or crystals.
If there is a large amount of fluid in the joint (called an
effusion), your doctor may drain it to help relieve the pain and provide easier
joint movement. This may only provide temporary relief. It’s not unusual for
fluid to build up in the joint again.
What is a joint injection?
Your doctor may also decide to perform a joint injection.
In this procedure, your doctor injects a drug into the joint to help provide
more lasting relief of the pain and swelling. The drugs most commonly used for
this purpose are anti-inflammatory medications called corticosteroids (or steroids).
How do steroids work?
Steroids work by reducing the activity of the immune system.
They reduce the production of the chemicals that your white blood cells produce.
By slowing down the immune system, steroids can help reduce inflammation and
minimize the tissue damage that an overactive immune system can cause.
When administered locally, such as to a certain joint via an
injection, steroids can help relieve pain and swelling with a low risk of side
effects. However, steroid injections won’t work for everyone, and they shouldn’t
be used too often. Most doctors recommend no more than four injections per year
to a specific joint. Giving steroid injections more often, or injecting too much
medicine into the joint, is thought to speed up aging of the joint or to weaken
tendons or ligaments around the joint.
Which joints can be affected?
Joints that are the most likely to become painful and inflamed,
and that may benefit from steroid injection, include shoulders, wrists, hips,
and knees, but practically any joint can be affected and injected.
How safe are the procedures?
Joint aspiration and injection are generally very safe.
Infection is possible, but very rare, occurring in about 1 of every 2,000 to
15,000 injections. Your doctor will carefully wash the injection area with an
antibacterial medicine before inserting the needle. The tip of the needle may
damage cartilage inside the joint, but this is also very rare.
Other side effects can include allergic reactions to the
anesthetic or steroid preparation. Post-injection flares consisting of joint
swelling and pain several hours after the injection are rare and usually subside
within hours to days. Significant bleeding at the site or into the joint is also rare.
Does it hurt?
Discomfort from the pinprick of the needle is generally very
tolerable, especially considering the potential long-term reduction in joint
pain. Your doctor may numb the area (local anesthesia) before inserting the needle.
If your doctor is going to perform both a joint aspiration and a joint injection, he or
she can usually do this through the same needle, without removing and reinserting it. In most
cases, the entire procedure takes just a few minutes.
How long will an injection work?
This depends on the patient and how bad the inflammation is.
Sometimes the relief is long-lasting or even permanent; in other cases, it may
only help for a few days or weeks. You should tell your doctor right away if the
pain and swelling return very soon after an injection.
Is there anyone who shouldn’t get an injection?
Yes. Some people may be allergic to the anesthetic or steroid
preparation. Also, if the joint has a fracture or an infection, that condition
must be taken care of before a steroid injection can be given.
What is viscosupplementation?
Some people who have constant pain in their knees have a
condition called osteoarthritis. Unlike the temporary pain and inflammation
caused in a joint by an overactive immune system response, osteoarthritis is a
degenerative joint disease.
Osteoarthritis mostly affects the cartilage. Cartilage is the
tissue that covers the ends of bones in a joint. When healthy, cartilage allows
bones to glide over one another and provides a "shock absorber" function. The
normal knee joint also contains a small amount of fluid called synovial fluid,
which is a thick, gel-like substance that cushions the joint and provides
lubrication to reduce friction.
In osteoarthritis, the surface layer of cartilage breaks down
and wears away. Adding to the problem, the synovial fluid in your knees loses
its ability to lubricate the joint. This combination causes pain and stiffness,
limitation of joint motion, and some inflammation in your knees.
Viscosupplementation is a procedure in which a thick fluid
called hyaluronate is injected into the knee joint. There are no cures for
osteoarthritis, so viscosupplementation will not cure osteoarthritis of the
knee. However, it is thought that hyaluronate will improve the lubricating
properties of the synovial fluid, reduce the pain from osteoarthritis of the
knee, improve mobility, and provide a higher and more comfortable level of activity.
Viscosupplements are usually reserved until other treatment options have been tried to
relieve your pain. Three to five injections, each 1 week apart, are required.
Not all patients are helped by the injections. Of those who are,
many report feeling some pain relief during the 3- to 5-week course of the
injections, while pain relief is delayed in others. Most patients report the
greatest pain relief 8 to 12 weeks after beginning treatment. The length of pain
relief varies; some patients have reported benefits for more than 6 months
following the injections.
The most commonly reported side effects associated with the
injections are temporary injection-site pain; swelling, heat, or redness; rash
and itching; bruising around the joint; and fluid accumulation in the injected
knee. These reactions are usually mild and don’t last long. As with steroid
injections, infection and bleeding are also rare complications.
Talk to your doctor about viscosupplementation if you have
osteoarthritis and have not found pain relief from other means such as exercise,
physical therapy, weight loss, use of heat and cold, use of a cane or other
product that relieves pressure on the knee, use of pain relievers, or steroid
injections.
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