Knee Joint Aspiration and Injection


OVERVIEW

CRITERIA FOR THE CLASSIFICATION OF OSTEOARTHRITIS OF THE KNEE USING CLINICAL AND LABORATORY FINDINGS
The patient should complain of knee pain and at least 5 of the following 9 features:
  • Age >50 yr
  • Stiffness <30 min
  • Crepitus
  • Bony tenderness
  • Bony enlargement
  • No palpable warmth
  • ESR <40 mm/hr
  • Rheumatoid factor <1:40
  • Synovial fluid signs of osteoarthritis (clear to straw-colored, high viscosity, 1,000 - 7,500 WBC, 2.9-5.5 g of protein/dL)
RECOMMENDED TESTS FOR SYNOVIAL FLUID
Always perform:
  • Note the volume and gross appearance of the fluid
  • Total WBC and differential
  • Conduct polarized light examination
  • Wet preparation
  • Gram stain and culture (if indicated by the clinical situation or previous examinations)
Defer these tests (unlikely to yield useful information):
  • Viscosity or mucin clot
  • Red blood cell count
  • Protein, glucose
  • Complement, immune complexes, rheumatoid factor, antinuclear antibody

 

INDICATIONS
  • Diagnostic evaluation of the cause of an effusion or an unexplained monoarthritis
  • Diagnostic evaluation of traumatic effusion (evaluate for hemarthrosis or fat in the effusion)
  • To limit joint damage from infected or inflamed joint fluid by serial removal of fluid
  • Symptomatic relief by removing a large effusion or treatment of joint pain or inflammation
  • Diagnosis or treatment of a crystal-induced arthropathy
  • Administration of viscous agents for symptomatic improvement of osteoarthritis
CONTRAINDICATIONS
Relative:
  • Bacteremia OR overlying cellulitis over the joint
  • Bleeding diathesis or coagulopathy
  • Uncooperative patient
  • Injection of steroids if septic arthritis is suspected or present
  • Clinician is unfamiliar with the correct approach to any joint
  • Presence of a joint prosthesis
TECHNIQUE


(1) Anatomic structure of the knee

With the patient lying supine, the suprapatellar pouch can be milked with downward pressure to reveal fluid that may not be apparent during the initial examination (Figure 2A). Alternately, the patella can be balloted with direct downward pressure.

(2) Checking for a joint effusion
Direct injection into the joint can be achieved under the patella with the knee flexed 90 degrees.

(3) Direct injection into the joint can be achieved under the patella with the knee flexed 90 degrees

PITFALL: This technique is discouraged, because the needle tip may cause damage to the articular surfaces or the menisci. This direct approach may be acceptable when administering therapeutic viscous solutions (e.g., hyaluronic acid), because the knee cartilage has previously received significant wear.

The superolateral technique uses an entry point 1 cm lateral and 1 cm superior to the upper lateral point on the patella (Figure 4A). This entry site can be approximated by measuring 1 fingerbreadth laterally and superiorly.


(4) The superolateral technique uses an entry point 1 cm lateral and 1 cm superior to the upper lateral point on the patella

The needle is inserted through skin stretched with the nondominant hand to reduce the patient's discomfort. Alternately, some physicians infiltrate 1% lidocaine (without steroid) to the skin entry site before the arthrocentesis needle is inserted.





(5) The needle is inserted through skin stretched with the physician's non-dominant hand to reduce the patient's discomfort

The aspirating syringe (60, 20, or 10 mL) is attached to a 20- or 22-gauge, 1 1/4-inch needle. The needle is cross-clamped with a sterile hemostat (i.e., perpendicular to the long axis of the needle) at the needle base.


(6) The needle is cross-clamped with a sterile hemostat.

The needle is gently inserted beneath the patella at a 45-degree angle to the axis of the extremity, aiming the needle to the center of the joint at the inferior portion of the patella.

(7) Insert the needle gently beneath the patella at a 45-degree angle to the axis of the extremity.

PITFALL: The needle tip should pass easily and not touch nearby structures. Touching the needle to any structures within the joint can cause significant discomfort

After aspiration of fluid, the needle is held steady with the hemostat. The Luer-lock syringe is detached from the needle using counter-clockwise rotation (Figure 8A), and the syringe with steroid and lidocaine is reinserted rapidly without contaminating the needle. The injecting syringe is locked onto the needle using a clockwise rotation (Figure 8B). Inject the 1 mL of steroid (6 mg of betamethasone or 40 mg of triamcinolone) with 3 to 7 mL of 1% lidocaine. The needle is then removed, and a sterile bandage is applied to the injection site.



 

(8) The Luer-lock syringe is detached from the needle, and the syringe with steroid and lidocaine is reinserted rapidly without contaminating the needle.

PITFALL: Avoid movement of the needle when removing or reapplying a syringe. Movement of the needle is very painful.


 

 INSTRUMENT AND MATERIALS ORDERING
The following instruments and materials are needed:
  • Sterile gloves
  • Sterile fenestrated drape
  • 10-mL syringe (for administering lidocaine and steroid)
  • 30-mL syringe x 2 (for aspirating effusion; can use a second 10-mL syringe if the effusion is small)
  • Two 21-gauge, 1 1/4 inch needles (one to draw up injecting solutions, one for performing arthrocentesis)
  • 1 inch of 4 x 4 gauze soaked with povidone-iodine solution for skin preparation
  • Hemostat for stabilizing the needle when exchanging medication syringe for aspiration syringe
  • Post-procedure bandage