College of Veterinary Medicine

Small Animal DX & Therapeutic Techniques

Collection of Joint Fluid: Arthrocentesis 

Arthrocentesis can generally be performed with light sedation of the animal. Obviously distended joints should be aspirated. If the patient displays signs of a polyarthropathy, without apparent joint swelling, multiple joints should be tapped. The joints that are easiest to tap include: carpi, stifles, and shoulders. The hair should be shaved over the joint and the skin cleansed with an antiseptic solution. Sterile gloves should be worn. A 20 gauge needle and 3 ml syringe are used. Arthrocentesis of the stifle joint can be performed either medial or lateral to the straight patellar ligament. The joint is flexed. Digital pressure on the opposite side of the patellar ligament will distend the joint. The point of entry is approximately midway between the proximal aspect of the patella and the tibial tuberosity. The needle is directed toward the intercondylar space.

arthro_carpus.jpg (26859 bytes)

The carpal joint can be entered at the radiocarpal or intercarpal joint on the anterior surface of the joint. Flex the carpus to widen the joint spaces. The needle is inserted perpendicular to the joint. Enter the joint without pulling back on the plunger of the syringe. Aspirate when the needle is in the joint. Joint fluid is viscous and will flow slowly into the syringe.

Unless the joint is markedly distended, expect to obtain a few drops up to a few tenths of a ml from the carpal joint. Stop aspirating before removing the needle from the joint, to prevent contamination of the joint fluid with blood from adjacent tissues. The sample is smeared on slides or if sufficient in volume, placed in an EDTA tube for cytologic analysis. A portion of the sample can be saved for possible bacteriologic culture, depending upon cytologic results.


The shoulder joint is aspirated from the lateral side of the joint. Run your finger down the spine of the scapula until you reach the acromion. The needle is inserted just distal to the acromion

Last Edited: Jan 28, 2009 3:28 PM   

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