Background
Arthrocentesis (synovial fluid aspiration) of the knee can be performed either diagnostically (for identification of the etiology of acute arthritis) or therapeutically (for pain relief, drainage of septic effusion, or injection of medications).[1, 2]
To avoid puncture of tendons, blood vessels, and nerves, the clinician performing the procedure should be familiar with the anatomy of the specific joint. The risk of such injuries can be minimized by using the extensor surface of the joint for needle insertion while keeping the joint in minimal flexion.
Indications
Indications for diagnostic knee arthrocentesis include the following:
- Evaluation of monoarticular arthritis
- Evaluation of suspected septic arthritis
- Evaluation of joint effusion
- Identification of intra-articular fracture and ligamentous tear
- Identification of crystal arthropathy
Indications for therapeutic knee arthrocentesis include the following:
- Relief of pain by aspirating effusion or blood
- Injection of medications (eg, corticosteroids, antibiotics, or anesthetics)
- Drainage of septic effusion
Contraindications
There are no absolute contraindications for knee arthrocentesis. Relative contraindications include the following:
- Suspected septic joint - In this case, no contraindications exist
- Cellulitis overlying the joint - If arthrocentesis is performed, the patient should be admitted for the administration of intravenous (IV) antibiotics, even if the synovial fluid is not suggestive of infectious arthritis
- Skin lesion or dermatitis overlying the joint
- Known bacteremia
- Adjacent osteomyelitis
- Uncontrolled coagulopathy
- Joint prosthesis – Preferably, a joint prosthesis is tapped by an orthopedist
Siva C, Velazquez C, Mody A, Brasington R. Diagnosing acute monoarthritis in adults: a practical approach for the family physician. Am Fam Physician. Jul 1 2003;68(1):83-90. [Medline]. [Full Text].
Zuber TJ. Knee joint aspiration and injection. Am Fam Physician. Oct 15 2002;66(8):1497-500, 1503-4, 1507. [Medline]. [Full Text].
Self WH, Wang EE, Vozenilek JA, del Castillo J, Pettineo C, Benedict L. Dynamic emergency medicine. Arthrocentesis. Acad Emerg Med. Mar 2008;15(3):298. [Medline].
Thomsen TW, Shen S, Shaffer RW, Setnik GS. Videos in clinical medicine. Arthrocentesis of the knee. N Engl J Med. May 11 2006;354(19):e19. [Medline].
[Best Evidence] Margaretten ME, Kohlwes J, Moore D, Bent S. Does this adult patient have septic arthritis?. JAMA. Apr 4 2007;297(13):1478-88. [Medline].
Li SF, Cassidy C, Chang C, Gharib S, Torres J. Diagnostic utility of laboratory tests in septic arthritis. Emerg Med J. Feb 2007;24(2):75-7. [Medline].
McGillicuddy DC, Shah KH, Friedberg RP, Nathanson LA, Edlow JA. How sensitive is the synovial fluid white blood cell count in diagnosing septic arthritis?. Am J Emerg Med. Sep 2007;25(7):749-52. [Medline].
Reichman and Simon. Emergency Medicine Procedures. 1st. New York: McGraw Hill; 2004.
| Appearance | WBCs, cells/µL | PMN cells | Glucose concentration, mg/dL | Protein concentration, g/dL | |
| Normal | Clear | < 150 | < 0.25 | Serum glucose | 1.3-1.8 |
| Noninflammatory | Clear | < 3000 | < 0.25 | Serum glucose | 2-3.5 |
| Inflammatory | Cloudy | >3000 | < 0.75 | < 25 | >4 |
| Purulent | Cloudy | >50,000 | >0.9 | < 25 | >4 |
| Hemorrhagic | Bloody | >2000 | ~ 0.3 | Serum glucose | … |
| PMN = polymorphonuclear; WBC = white blood cell. | |||||
Print
