Joints are connections between two or more bones. They allow us to move our bodies. If a joint is swollen or inflamed due to an injury or disease, more fluid may build up inside it. The medical term for this is "joint effusion."
Joint aspiration involves using a thin hollow needle to take some of the fluid out of the joint. This procedure, also known as arthrocentesis, is one of the more common procedures used for muscle and bone problems. It is most often done at the knee or shoulder.
When is joint aspiration necessary?
If a joint is swollen, analyzing a sample of joint fluid (synovial fluid) can help to find the cause of swelling. Even the color can be used as a first indication of what is wrong: Fluid from a healthy joint is usually clear. The fluid inside an injured joint is often a bloody reddish color, and the fluid inside an inflamed joint is usually cloudy. The sample of fluid can be tested to find out whether, for instance, it contains bacteria or abnormally high levels of white blood cells.
Aspiration may also be used as a treatment – to reduce the pressure on the joint, for example. Then the doctor uses the syringe to remove the excess fluid. If needed, medication can be injected into the joint during joint aspiration.
What happens during the procedure?
Special preparation is usually not needed. The surrounding skin is carefully disinfected beforehand to stop germs from entering the joint. Sometimes the area is covered with a sterile cloth too. The doctor wears sterile disposable gloves, and usually a surgical gown, a surgical mask and a cap. Sterilized disposable cannulas and syringes are unpacked right before use.
Joint aspiration typically feels a bit like having blood drawn. A local anesthetic is usually not needed, but a numbing gel or spray may be used. The doctor can use ultrasound to locate the position of very small or deep joints, and will then mark the right spot for inserting the needle on your skin. Sometimes, the entire procedure is monitored using ultrasound.
If necessary, the fluid that is removed is sent to a laboratory in a tube for analysis. A pressure bandage is often applied after the procedure. The joint itself usually needs to be kept still – how long will depend on the cause of the swelling and whether medication was injected during the aspiration. Afterwards it is important to watch carefully for signs of infection. If the joint or puncture site are red, swollen or start feeling very warm, you should inform your doctor immediately. Other warning signs include fever and worsening pain.
What are the associated risks?
The doctor should explain the procedure and associated risks in as much detail as possible before carrying out the joint aspiration.
There may be bleeding in the joint afterwards. Inflammation where the needle was inserted is also possible. If medication is injected, it may cause a feeling of pressure or a short burning sensation. The medication might have side effects such as allergic reactions too. Anti-inflammatory drugs can lead to a red face, increased blood pressure, a racing heartbeat and also make you feel hot.
The greatest risk is that of an infection caused by germs that have got into the joint. This risk of this happening varies, depending on what is done during the aspiration and which joint is involved. Diseases like diabetes or a weakened immune system increase the risk of infection.
Joint aspiration is not advisable if you have an inflammation, wound or skin condition near the site of needle insertion. This greatly increases the risk of infection.
IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.
Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. informedhealth.org can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.
Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.
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