What is Arthrocentesis?
Arthrocentesis involves withdrawing (aspirating) a small sample of joint fluid from a joint using a needle and syringe by carefully inserting them into a joint space excess fluid is removed and can be evaluated for suspected joint disease or conditions. Mr. Ryals can perform Athrocentesis on any joint of the foot, with some joints being more difficult than others (See Picture 1). The most common joints for Athrocentesis are the ankle and big toe joints. Joint aspiration is diagnostic and therapeutic, helping to relieve pain and swelling caused by excessive joint fluid by decreasing pressure within the joint to improve joint movement. The aspirated fluid is called synovial fluid which is normally slippery and viscous. A small amount of synovial fluid is found in most joints. The fluid, along with cartilage, facilitates smooth joint movement and provides cushioning between the joint's bones. Synovial fluid's composition can change over time and reflects the relative health of joints.
Picture 1 - A needle guided into the Calcaneocuboid joint to perform Athrocentesis via Ultrasound.
Arthrocentesis is typically done for one of three reasons:
1. Take make a diagnosis (Infection, disease process, bursitis)
2. Alleviate pressure and pain in a joint.
3. Enable an additional therapeutic drug to be injected (Corticosteroid or viscosupplementation).
The synovial fluid that is collected during arthrocentesis may undergo analysis to aid in diagnosis and treatment.
Mr. Ryals will explain the procedure. You will be asked to sign an informed consent form to make sure you understand the procedure, risks, benefits and more importantly to gain your permission to perform the procedure. Before arthrocentesis, patients should tell Mr. Ryals of any:-
- Known allergic reactions
- Known infections or blood/bleeding disorders
- Known to be pregnant
Patients taking blood thinners or anticoagulants may be asked to stop taking these medications in the days leading up to arthrocentesis, whilst others may still take these medications but the aspiration site will need extra care and rest.
The procedure takes 5-10 minutes. You will be positioned on an examination table and the joint sterilised. The injection site is marked and a sterile needle carefully inserted into the joint where fluid will be drawn from the joint. Occasionally medical imaging may be used to help guide the needle into the joint. An aenesthetic or numbing agent may be sprayed onto the skin to help alleviate pain of the injection, sometimes both are used. The collected fluid will be either analysed or destroyed. Arthrocentesis can be followed with a corticosteroid or viscosupplementation injection the needle will remain in the joint whilst this is being performed. A sterile dressing will be placed over the aspiration site once finished.
What to Expect
The effects of athrocentesis vary but its considered a safe procedure with few side effects. Some patients may resume activities immediately, whilst others may have to rest. Mr. Ryals may use lignocaine (local anaesthetic) whilst performing athrocentesis which typically wears off in 2 to 4 hours so pain may occur after the procedure. Mild soreness for a day or two after the procedure is common and managed with anti-inflammatory of icepacks. Very rarely a patient may experience an allergic reaction to the anaesthetic or in extremely rare cases an infection may be introduced into the joint.
Mr. Ryals may decide not to perform a joint aspiration if the patient has:-
- A known infection
- Bleeding disorders
- Poor joint accessibility