Arthrocentesis is typically a quick in-office procedure. In fact, a doctor may recommend arthrocentesis be done immediately, without setting up a separate appointment.
Other times, the procedure will be scheduled in the future and the patient may need to make preparations.
Who will perform this procedure? See Arthritis Treatment Specialists
Preparing for Arthrocentesis
Before arthrocentesis, patients should tell the doctors if they:
- Take any medications, including over-the-counter medicines and herbal supplements
- Are allergic to any medications, latex, or anesthesia
- Have any kind of infection, or a blood or bleeding disorder
- Are or could be pregnant
Some patients who take blood thinners or anticoagulants may be asked to stop taking these medications in the days leading up to arthrocentesis.
Other patients may continue to take these medications but will need give the aspirated joint a little extra care, such as applying direct pressure to the needle site and resting the joint for a little longer than normal.
Patients who will undergo general anesthesia and patients whose joint fluid will be tested for glucose levels may need to fast before arthrocentesis. Most patients do not need to fast.
Patients may also want to ask their doctors if arthrocentesis will affect their ability to drive or do other essential tasks in the hours following the procedure. For example, a patient whose right knee joint is aspirated may need someone to drive him or her home.
Arthrocentesis (Joint Aspiration) Procedure
Arthrocentesis is an in-office procedure that typically takes just 5 to 10 minutes. The steps are as follows:
- The patient is asked to sit or lie down in a position that is comfortable and gives the doctor easy access to joint. For example, when aspirating the knee, the patient is asked to recline with the leg relaxed and straightened or at a slight angle. If the knee is at an angle, a towel may be put underneath the knee for support.
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- The doctor will use a pen to mark the spot where the needle puncture is to be made.
- The skin around the needle puncture site is thoroughly cleaned.
- Occasionally, a doctor will use ultrasound or other medical imaging to help guide the needle into the joint space.1
- If ultrasound is being used, a gel will be applied to a small area of skin near the needle puncture site, and a technician will gently press a hand-held ultrasound transducer against the gel-covered skin. An image of the joint space will be projected onscreen for the doctor to see.
- An anesthetic such as lidocaine may be injected or a numbing agent called ethyl chloride may be sprayed onto the skin. Sometimes both an injectable anesthetic and a topical agent will be used.
- General anesthesia or a sedative may be used if the joint being aspirated is deep (e.g. hip) or if the patient is particularly anxious or cannot remain still and relaxed for the procedure (e.g. a child).
- Once the area is numbed, the doctor will enter a needle into the affected joint or bursa. The needle will have an attached syringe. As the doctor pulls back on the syringe’s plunger, the syringe will fill with joint fluid.
- If arthrocentesis is to be followed by a corticosteroid injection or viscosupplementation, then the needle may remain in the joint while the syringe containing joint fluid is gently detached and a new syringe filled with medication is attached. The medication is then injected into the joint.
- Medication should not be injected unless there is already a certain diagnosis.
- The needle is withdrawn and the area is bandaged.
The procedure may be uncomfortable but this discomfort should be short-lived. Once it is complete, the sample of joint fluid (synovial fluid) may undergo analysis. A patient should ask his or her doctor when and how the lab results will be made available.