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Joint Aspirations

Specialist soft tissue and joint injection physiotherapists can perform joint aspiration procedures to relieve excess fluid build up in a swollen joint or bursa. The knee is probably the most commonly swollen joint in the body, and many patients come to see us with significant knee inflammation. This video will really help you to see what the process is like:

Knees are very prone to swelling and pain because they are weight-bearing joints. The swelling occurs when fluid builds up in or around your knee joint. This is sometimes called water on the knee but is medically called an effusion. The most common causes are overuse, injury or trauma, underlying degenerative changes and osteoarthritis.

Before we do an aspiration, we will take case history to understand how the swelling started, how long the swelling has been present for, and enquire about other underlying medical conditions. We will want to know about previous knee injuries and treatments/surgeries, and what hobbies or sports you play, what makes your knee pain or swelling worse, and things that make it better.

After the case history, we will do a thorough physical examination. During this time, we might ask you to do a squat or another movement such as bending one leg. We will ask you to lie down on the treatment table so that we can assess your knee joint and feel for pockets of swelling.

We will explain the procedure in detail, so you understand more about the process. We will give you every opportunity to ask questions about the procedure, the risks, and benefits. If you agree and consent to have the aspiration done, then we will go ahead.

As with any invasive procedure, there is always a risk of infection although this is rare, and we will do everything we can to ensure the procedure is aseptic and safe. The procedure can be painful during as well as afterwards, but we will do everything we can to minimise this including administering a local anaesthetic if clinically appropriate and safe to do so. It is advisable to have someone bring you to the appointment and take you home. There is sometimes a small bleeding that occurs at the skin where the injection goes in, especially if you are on blood thinners, so it is important to ensure that your blood thinning medication is working for you (this would be in consultation with your GP).

Often we inject a corticosteroid to help settle the inflammation and prevent the joint from swelling up again. There are some risks associated with this medication:

  • Immunosuppression (steroids temporarily lower your immunity and theoretically put you at more risk of an infection).
  • Joint and soft tissue damage (this is very rare and is mainly caused by having repeated steroid injections into the same joint too often over a short time period).
  • Facial flushing and tingling (this is a fairly common reaction to steroids and is temporary lasting a few days at the most).
  • Steroids can raise your blood sugar levels, so it is important that if you are diabetic, it is a well-controlled condition.
  • Total knee replacement or unilateral knee replacement
  • Recent trauma to the joint
  • Recent or current infection
  • Recent vaccination (less that 14 days)
  • Pregnancy and breast feeding
  • Uncontrolled diabetes
  • Immunosuppression

In most cases, we draw out excess synovial fluid, also known as joint fluid, which is a thick viscous liquid located between your joints. Knee joints normally have around 6-10 ml of synovial fluid. This fluid cushions the ends of bones and reduces friction when you move your joints. Inflammation of the knee can result in a significantly larger volume of fluid in the joint causing pain and reduced function. The picture below is 140ml of fluid taken from a 59-year-old woman’s right knee.

Needless to say, she felt immediate improvement! Bare in mind it’s very unusual to draw out this level of fluid and we might draw out anywhere between 10 ml and 30 ml as a rough guide. Sometimes we aspirate blood mixed with synovial fluid. This happens after trauma to the knee, and an example can be seen on the video at the top of the page.

Very rarely, the fluid aspirated may appear infected. In this case we will advise you on seeking urgent medical attention for further investigations.

Straight away patients typically report a feeling of relief in their knee. This is usually because the excess fluid puts a lot of hydrostatic pressure on the joint. Excess fluid also reduces movement. Imagine a swollen knee and you will know that the joint will be stiff. When the fluid is removed, the knee is able to bend further. Most patients report walking significantly better following an aspiration.

Aspiration is often difficult to get done on the NHS. We have had many patients report attending Accident and Emergency with a large joint effusion but not had their knee aspirated. This is because it is not a medical emergency. Some GP practices may have a doctor or other specialised clinician who specialises in soft tissue and joint injection therapy and may be able to do the procedure for you, so enquire at your surgery first. If you are referred to orthopaedics, an aspiration can be done by an orthopaedic consultant, but there are very long waits currently for orthopaedic referrals.

At Farnborough Physio we charge £150 for an aspiration which will be undertaken by Ben Coffey. This includes the consultation fee. If it is necessary to also inject a local anaesthetic and corticosteroid, the cost is £185 for the procedure.