joint aspiration
joblist: technique
Midpoint approach: 1 cm lateral or medial to the patella, directing the needle posterior and horizontal toward the intercondylar notch of the femur.
Infrapatellar approach: With knee flexed to 90°, needle inserted 5 mm below the patella’s inferior border, posterior to the patellar tendon
Complications
Local trauma, pain, infection, dry tap
Haemoarthrosis - usually self-limiting
interpretation
| Type | Colour & Clarity | WBCs (cells/mm3) | Neutrophils (%) | Viscosity | Crystals | Culture |
|---|---|---|---|---|---|---|
| Normal | Clear colourless | < 200 | < 25 | High | Neg | Neg |
| Non-inflammatory e.g. Osteoarthritis | Clear yellow | 200 - 2000 | < 25 | High | Neg | Neg |
| Inflammatory (e.g. Rheumatoid arthritis) | Cloudy yellow | 2000 - 50000 | ≥ 50 | Low | Pos (gout/pseudogout) | Neg |
| septic arthritis | Cloudy yellow/green | > 50000 | ≥ 75 | Low | Neg | Pos |
| Haemorrhagic | Bloody red | 200 - 2000 | 50-75 | Variable | Neg | Neg |