Should an effusion be aspirated prior to injecting hyaluronic acid (HA) into the knee?

From the Guidelines

Yes, you should aspirate a knee effusion prior to injecting hyaluronic acid. When a significant effusion (excess fluid) is present in the knee joint, it should be drained before administering the hyaluronic acid injection. This aspiration serves multiple purposes: it relieves pressure within the joint, potentially providing immediate symptom relief; it creates space for the hyaluronic acid to be distributed properly within the joint; and it allows for analysis of the synovial fluid if needed for diagnostic purposes.

The procedure involves inserting a needle into the joint space, typically from a lateral approach with the knee in extension, withdrawing the excess fluid, and then injecting the hyaluronic acid using either the same needle (after changing the syringe) or a new needle insertion. Failure to remove a significant effusion before injection may dilute the hyaluronic acid, potentially reducing its effectiveness and therapeutic duration. Additionally, mixing hyaluronic acid with inflammatory synovial fluid could theoretically diminish its viscoelastic properties.

According to the most recent EULAR recommendations 1, the aim of intra-articular therapies, such as hyaluronic acid injections, is to improve patient-centered outcomes, including benefits, harms, preferences, or implications for self-management. Aspirating the effusion prior to injection aligns with this goal by potentially enhancing the effectiveness of the treatment and minimizing complications. The EULAR recommendations also emphasize the importance of considering contextual factors, such as effective communication and patient expectations, which may influence the outcome of intra-articular therapies 1.

Key points to consider when aspirating a knee effusion prior to injecting hyaluronic acid include:

• Using sterile technique to minimize infection risk
• Analyzing the synovial fluid for diagnostic purposes if needed
• Creating space for the hyaluronic acid to be distributed properly within the joint
• Potentially enhancing the effectiveness of the treatment by removing inflammatory synovial fluid
• Aligning with the EULAR recommendations to improve patient-centered outcomes 1.

It is essential to note that the evidence for the effectiveness of hyaluronic acid injections in knee osteoarthritis is relatively small, and the size effect is relatively small, as mentioned in the EULAR recommendations 1. However, aspirating the effusion prior to injection is a crucial step in optimizing the treatment outcome.

From the FDA Drug Label

Dosage and Administration: ... Excess synovial fluid should be removed prior to injection.

• The recommended procedure is to remove excess synovial fluid, which can be interpreted as aspirating an effusion, prior to injecting hyaluronic acid into the knee.
• This suggests that aspiration of the effusion is advised before administering the final dose of hyaluronic acid 2.

From the Research

Aspiration Prior to Hyaluronic Acid Injection

• The decision to aspirate an effusion prior to injecting hyaluronic acid into the knee is a topic of discussion among medical professionals, with some studies suggesting its benefits and others indicating its limitations 3, 4, 5.
• A study published in 2014 found that aspiration exhibited a temporary improvement in clinical parameters, especially in post-traumatic effusion, but this improvement lasted only for the first week due to early re-accumulation of the effusion 3.
• Another study published in 2016 found that synovial fluid aspiration before hyaluronan injection significantly improved pain and function scores in patients with knee osteoarthritis 4.
• The volume of synovial fluid present in the joint can affect the efficacy of viscosupplementation, with interpatient variation in volume potentially explaining some of the observed variations in efficacy 5.

Clinical Implications

• Aspiration may be beneficial in establishing a diagnosis in cases of unknown origin and providing immediate clinical relief 3.
• However, aspiration should be performed with consideration in the presence of trauma 3.
• The use of hyaluronic acid injections for knee osteoarthritis treatment has been evaluated in various studies, with some indicating its effectiveness in reducing subjective symptoms and improving clinical outcomes 4, 6, 7.
• Appropriate use criteria for hyaluronic acid in the treatment of knee osteoarthritis have been developed to guide clinical decision-making and ensure effective use of this treatment option 7.

Key Findings

• Aspiration before hyaluronic acid injection may improve clinical outcomes, including pain and function scores 4.
• The presence of synovial fluid can affect the efficacy of viscosupplementation, highlighting the importance of considering joint effusion in treatment planning 5.
• Hyaluronic acid injections can be an effective treatment option for knee osteoarthritis, with benefits including reduced pain and improved function 4, 6.