What Is Joint Aspiration (Arthrocentesis)?

Joint aspiration (arthrocentesis) is a diagnostic procedure that involves the extraction and analysis of the synovial fluid in the joints. It is an important procedure used for diagnosing arthritis and differentiating inflammatory arthritis from noninflammatory arthritis. 

Joint aspiration is a relatively quick and inexpensive procedure to perform. It can be done in a clinic or hospital. Any trained physician, physician’s assistant, or nurse can perform the procedure.

Joint aspiration may be indicated for any patient with an inflamed joint or joints that do not have an established diagnosis. Inflamed joints are recognized by being red, warm, tender, swollen, and painful during movement. 

Some conditions that may require joint aspiration and analysis are:

• Acute and chronic arthritis
• Rheumatoid arthritis 
• Gout
• Septic arthritis (infection of the joint)

Joint aspiration may be performed as a treatment in certain conditions, such as:

• Repeated aspirations can be part of the management of the septic joint to relieve discomfort and prevent joint damage.
• Aspiration can be considered in cases of hemarthrosis (blood in the joints) to prevent adhesions. 
• Aspiration can be performed while injecting intra-articular medications such as corticosteroids or hyaluronic acid to improve efficacy. Steroid injections help reduce joint inflammation, reduce pain, preserve joint structure, and function. Hyaluronic acid lubricates the joint, decreases impact, delays joint aging, and reduces pain and stiffness.

Joint aspiration should be performed with caution in patients with a bleeding disorder or those on anticoagulant drugs. Patients taking anticoagulant drugs may be advised to stop the medications a few days before the procedure and resume again after the procedure.

Any joint in the body can be aspirated. Some joint aspirations require the use of radiological guidance, as it may be required to confirm the presence of fluid before aspirating. Radiological imaging can help aspirate deep and technically difficult joints like the hip joint or spine. 

Joint aspiration is a relatively quick procedure but may be performed under local anesthesia to avoid pain. 

• A sterile needle of appropriate size and length is introduced into the joint and the synovial fluid is collected in syringes. 
• The fluid collected is then analyzed microscopically. 
• Apart from microscopic analysis, the appearance of the aspirated synovial fluid can indicate certain features. 
• Normal fluid is clear or light yellow and viscous. 
• Inflammatory fluid appears darker yellow to cloudy and loses its viscosity. 
• Purulent fluid (pus in the fluid) is brownish to whitish and opaque.
• After the procedure, the patient is asked to rest for a few minutes, and then they can resume normal activities.
• Some patients may experience pain and bruising, which resolve in a few days. Ice packs and pain killers can help reduce pain and bruising.

Joint aspiration is a relatively safe procedure and complications are rare. The common complications are

• localized bleeding,
• pain,
• swelling, and
• sometimes a reaction to local anesthesia.

In rare cases, infection of the joint may occur, which is called septic arthritis. 

If medications like steroids are simultaneously injected, though rare, it may cause localized shrinkage or hypopigmentation of the skin. Long-term use of steroid injections may cause systemic side effects like

• weight gain,
• puffy face,
• stretch marks, and
• easy bruising.