Knee Arthrocentesis in Adults

Summary

Here the protocol describes arthrocentesis of the knee, a procedure in which a needle is inserted into the knee joint, and synovial fluid is aspirated. Synovial fluid may be removed for testing to determine the nature of the knee effusion. Arthrocentesis of the knee is typically performed with the patient supine.

Abstract

Arthrocentesis of the knee is a procedure in which a needle is inserted into the knee joint, and synovial fluid is aspirated. An arthrocentesis can be diagnostic or therapeutic. Synovial fluid may be removed for testing to determine the nature of the knee effusion. If septic arthritis is suspected, urgent arthrocentesis before initiation of antibiotic treatment is indicated. Moreover, arthrocentesis can also aid in diagnosing crystal-induced arthritis such as gout or pseudogout, or non-inflammatory arthritis such as osteoarthritis. Identifying the cause of the knee effusion can guide treatment. Furthermore, removing fluid from a knee can reduce intraarticular pressure to decrease pain and improve range of motion. There is no absolute contraindication to performing this procedure, but in selecting the needle entry site, an area of skin that is infected should be avoided. Therefore, caution should be exercised when a patient presents with suspected cellulitis over the knee joint to avoid the potential risk of causing iatrogenic septic arthritis. A knee that has undergone arthroplasty should be assessed for arthrocentesis by an orthopedic surgeon. Arthrocentesis of the knee is typically performed with the patient supine. The site for needle insertion is marked, and then the skin is disinfected. After a local anesthetic is administered, a needle is inserted along the pathway that was anesthetized. Synovial fluid is aspirated, and then the needle is withdrawn. Pressure is applied until any bleeding stops. The synovial fluid can be analyzed for infection and inflammation but cannot directly confirm a diagnosis of internal derangement or autoimmune causes of arthritis. In addition to the history and physical examination, laboratory findings and imaging can clarify the etiology of a knee effusion.

Introduction

Arthrocentesis is performed to successfully aspirate synovial fluid from a joint such as a knee, shoulder, elbow, wrist, or ankle. A patient with a newly detected knee effusion can undergo a diagnostic arthrocentesis to determine the nature of the effusion. Before proceeding to attempt an arthrocentesis, knee swelling by history must be confirmed on physical examination to assess whether an effusion exists. With the patient supine, the knees can be compared on inspection to see if the swelling is unilateral. The knee with the effusion may appear larger than the other knee. With a large effusion (at least 20 mL), convexity can be seen proximal to the patella. With a sm....

Protocol

This protocol follows the guidelines at BronxCare Health System. A written informed consent is necessary from the patient.

1. Identifying anatomical structures

1. With the patient supine, carefully palpate the knee to locate the patella and use a skin marker to make marks at the four corners of the patella.
2. Place an "X" using a skin marker at a site that is one fingerbreadth superolateral to the patella. Avoid infected skin and visible veins.
<.......

Discussion

Knee arthrocentesis is a bedside or clinic procedure in which a needle is inserted into the joint capsule, and synovial fluid is aspirated. Before attempting an arthrocentesis, knee swelling by history should be confirmed to be an effusion on physical examination. A knee x-ray can reveal an effusion but is not necessary prior to aspiration. If body habitus complicates the physical examination, ultrasonography can be used to confirm effusion size and to direct insertion of the needle for aspiration⁸

Materials

Name	Company	Catalog Number	Comments
Alcohol prep pad	Medline	MDS090670Z	sterile 2-ply pad
Eclipse needle	BD	DGW60702	25G x 5/8"
Ethyl Chloride instant topical anesthetic spray	Gebauer's	P/N 0386-0008-03	non-flammable
Lidocaine HCl injection	Fresenius Kabi Usa, Llc	NDC 63323-492-27	1% single dose vial
Plastic bandage	Curad	CUR02278RB	4-sided seal
Plastipak 3 mL syringe	BD	309651	sterile
Plastipak 5 mL syringe	BD	309649	sterile
Povidone iodine topical solution	Major	NDC 0904-1103-09	topical antiseptic
Precision glide needle	BD	305196	18G x 1 1/2"
Sterile gauze sponge	CARING	PRM2208	2 in. x 2 in.
Sterile regular tip surgical skin marker	MEDLINE	DYNJSM01
Surgical gloves	TRIUMPH	MSG2265	sterile & powder-free