Joints are connections between two or more bones. They ensure the mobility of the body. If a joint is swollen or inflamed as a result of injury or illness, more fluid may accumulate inside it than usual. Then doctors speak of a joint effusion.
In a joint puncture, a small amount of fluid is removed from the joint with a fine hollow needle. Perforations are a standard intervention in muscle and bone diseases. Especially often the knee or shoulder joint is punctured.
When is a joint puncture necessary?
When a joint is swollen, examining the synovial fluid can help clarify the cause of the swelling. Even the color of the liquid can provide information: In a healthy joint, it is usually clear. In case of injury, it is generally bloody-red, cloudy in inflammation. Also, for example, it can be examined whether the extracted fluid contains bacteria or more white blood cells than usual.
Functions are also used for treatment, for example, to relieve the joint. To do this, the doctor removes the excess synovial fluid with the syringe. If necessary, the doctor can also inject a drug into the joint during the puncture.
How is the examination performed?
Special preparation is usually not necessary. To prevent germs from entering the joint, the skin around the puncture site before puncturing is thoroughly disinfected and sometimes covered with a sterile cloth. The doctor wears sterile disposable gloves, usually surgical gown, mask, and hood. The sterile packaged disposable cannulas and disposable syringes are opened just before puncture or injection.
Frequently, a puncture feels similar to a blood sample. A local anesthetic is usually not necessary, but it can be applied a locally anesthetic ointment or an ice spray. For very small or deep joints, the doctor can use an ultrasound to determine the position of the joint and mark the correct puncture or injection site on the skin. Sometimes the whole procedure is performed under ultrasound control.
If necessary, the withdrawn liquid is sent to the laboratory for analysis in a test tube. After the puncture sometimes a pressure bandage is applied. The joint usually needs to be immobilized – how long depends on the cause of the swelling and whether or not a drug was injected during the puncture. After a hole, it is crucial to watch for signs of inflammation. If the joint or the puncture site is reddened, swells or becomes hot, you should inform the doctor immediately. Warning signs are also fever and increasing pain.
What risks are there?
Before a joint puncture, the doctor must explain the intervention and possible risks in an informative discussion.
After a puncture, bleeding may occur in the joint. Also, inflammation at the injection site is possible. If drugs are injected, a feeling of pressure develops, sometimes even a short-term burning sensation. Besides, side effects such as an allergic reaction in anti-inflammatory agents, facial flushing, increased blood pressure, palpitations or heat sensation are possible.
The most significant risk is a joint infection due to introduced germs. The size of the risk depends on the type and location of the puncture. Diseases such as diabetes or immunodeficiency increase the risk of infection.
A joint puncture is not recommended if there is inflammation, a wound or skin disease in the area of the puncture site because then the risk of infection is unusually high.