From the Guidelines
When a knee joint aspiration is attempted but no fluid is obtained, the absence of fluid does not necessarily indicate the absence of infection, and further evaluation with imaging, blood cultures, and inflammatory markers is warranted. This is based on the most recent evidence from 1, which highlights the importance of considering alternative diagnostic approaches when a "dry tap" is encountered.
Key Considerations
- The absence of fluid on aspiration does not rule out infection, as emphasized by 1 and 1.
- Proper needle placement should be confirmed, and ultrasound guidance may be useful if available.
- If the needle is correctly positioned but no fluid is obtained, injecting a small amount of sterile saline and attempting to withdraw it can help confirm intra-articular placement.
- If clinical suspicion for infection remains high, consider further diagnostic steps such as MRI, ultrasound, or consulting orthopedics.
Diagnostic Approach
- Blood cultures and inflammatory markers (ESR, CRP) may be useful in the diagnostic workup when infection is suspected but no fluid is obtained on aspiration, as suggested by 1.
- Empiric antibiotics may be considered while awaiting further evaluation, especially if there is a high clinical suspicion of infection.
- The use of alpha-defensin testing in synovial fluid has been shown to be highly accurate in diagnosing periprosthetic joint infection, with sensitivity and specificity of 97% and 96%, respectively, as reported in 1.
Management
- Always document the attempted procedure, findings, and subsequent management plan.
- Consider repeat aspirations if the first attempt is negative and clinical suspicion for infection remains high, as recommended by 1.
- Intraoperative tissue sampling may be necessary if preoperative aspiration is negative but infection is still suspected, as noted in 1.
From the Research
Knee Joint Aspiration with No Fluid Aspirated
- The provided studies do not directly address the issue of knee joint aspiration with no fluid aspirated.
- However, a study on diagnostic abdominal aspiration 2 mentions that inability to obtain fluid, although in general reassuring, cannot be trusted absolutely, as there may be severe disease without aspirable exudate.
- This principle may be applicable to knee joint aspiration, suggesting that the absence of fluid does not necessarily rule out underlying pathology.
- The other studies provided focus on sepsis management 3, predicting aspiration without videofluorography 4, aspiration risk factors and microbiology in community-acquired pneumonia 5, and the use of antibiotics in treating aspiration pneumonia 6, which are not directly relevant to the topic of knee joint aspiration with no fluid aspirated.