Joint aspiration is the process of removing fluid usually from around a joint (most commonly the knee joint) is called joint aspiration. Joint aspiration is also known as arthrocentesis.
- Joint aspiration is a simple procedure that does not require hospitalization.
- The doctor will begin by rubbing an antiseptic over the joint to be aspirated.
- A local anesthetic will be administered.
- A needle will be inserted into the joint and the fluid is withdrawn.
- The entire procedure will be over in a matter of minutes.
Keep in Mind
Before the procedure, the doctor should be kept informed about any medical conditions you may have, including:
- Any bleeding disorder
- The use of any kind of blood thinner
- Any allergies
- Confirmed or possible pregnancy
After the Procedure
- The doctor will give detailed instructions on how to care for the aspirated area.
- Keeping the area dry is important.
- Keep the bandage on till the doctor approves its removal.
- Find out from the doctor when normal activities can be resumed.
- Take care not to put any undue pressure on the area.
- Slight pain after the procedure is expected; talk to the doctor about painkillers to handle the discomfort.
- A few pain killers like aspirin can increase bleeding so do not take anything without consulting the doctor first.
What to Watch Out for
- Fever of more than 100.4 F
- Increased pain around aspiration site
- The site is swollen and tender to touch
- Discharge from the aspirated area
If any of the above are experienced, the doctor must be informed immediately.
Reasons for Aspiration
- Joint Effusion
- Sometimes, fluid may collect around the joints due to an infection, trauma or arthritic changes.
- This fluid collection may cause pain and joint swelling.
- In such cases, the doctor may remove some fluid from the joint to relieve pain.
- This fluid may also be sent to the laboratory for further analysis.
- This analysis is very helpful in diagnosing arthritis – whether the arthritis is inflammatory or non – inflammatory.
Read Also: What are the Symptoms and Treatment for Arthritis?
- Joints have fluid-filled sacs called bursae around them.
- The bursae protect the joints and facilitate smooth, friction-free movement.
- Joint aspiration may be done for a condition called bursitis which is the inflammation of the fluid-filled bursae around the joints.
- To diagnose the reason for bursitis, aspiration can be done.
- By examining the fluid, the cause for bursitis (like gout or other conditions) can be established.
- This removal of fluid from the bursa is known as bursal aspiration.
Before an Injection to Treat Arthritis
- Treatment of arthritis may require an injection to the arthritic joint.
- Before giving the injection, the doctor may remove some fluid via joint aspiration, to increase the effectiveness of the injection given.
Analysis of the Fluid Withdrawn
The fluid is analyzed visually at first and the following characteristics are noted.
- Colour: The colour of the fluid is observed. When there is no infection, the fluid will be clear and colourless. When there is an infection present, the fluid will turn colloidal. A pink/red colour means blood has mixed with the fluid.
- Fluid Thickness: This is also known as viscosity. Normal fluid is usually quite viscous (thick). When infected, the fluid is less viscous and thin.
- Fluid Volume: If the volume of fluid present in the joint exceeds normal amounts by a significant margin, it indicates the presence of an infection.
Any abnormalities in the aforementioned factors mean there is a need for further analysis of the fluid. If these are found, a microscopic analysis must be done to determine the presence of the following ailments.
- Gout: When there are crystals of uric acid present in the fluid, it can mean the person is suffering from gout.
- Infectious Arthritis or Rheumatoid Arthritis: A high white blood cell (WBC) count is an indication for these two conditions.
- Bacterial Infection: The presence of microorganisms could indicate a bacterial infection and a culture analysis will be done to confirm this.
- Osteoarthritis: A high value of red blood cells (RBC) may be an indicator for osteoarthritis. RBC will also be high after an injury.
Evaluating the chemical composition of the fluid will aid in diagnosing arthritis. The following will help:
- The glucose level of the fluid will help in diagnosing both an infection and arthritis. The level will be lowered in both cases.
- The LDH enzyme level will be raised in case of rheumatoid arthritis, infectious arthritis and gout.
- An infection is suspected when the protein levels are high.
A microbiological analysis will also be done to ascertain the presence of bacteria and fungi. Normal fluid will not have any bacteria or fungi and hence when their presence is detected, it usually means an infection.
It should be noted that the aforementioned analyses alone are not sufficient to diagnose a condition. The doctor might also prescribe other diagnostic tests to arrive at a decision.
Joint Aspiration – Possible Side Effects
While reiterating that the procedure is very low risk, there are however some rare side effects that could occur.
- The cartilage might suffer a little damage due to needle insertion.
- Sometimes discolouration of the skin may be seen.
- The capsule surrounding the joint might get filled with blood.
- The skin might suffer irritation because of the antiseptic liquid used or the bandage applied after the procedure.
- In extremely rare cases, the joint might get infected.
Doctors agree that joint aspiration is a safe and speedy way of extracting fluid from a joint for treatment as well as diagnostic purposes.