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Knee Injection

  • Knee aspiration commonly is used for diagnostic purposes for effusions of unclear cause.
  • Injections are used most commonly to treat arthritis.
  • Indications
    • Effusion
    • Hemarthrosis
    • Infection/septic joint
    • Synovitis/arthritis
  • Equipment
    • 18-gauge needle
    • 20-60-mL syringes
    • Sterile gloves
    • Sterile antiseptic solution
  • Aspiration technique:
    • The superolateral approach is the most reliable for aspiration.
    • Position the patient supine on the examination table with the knee fully extended or with a pillow under the knee.
    • Perform a wide sterile preparation of the knee.
    • Identify the aspiration site ~1 finger breadth proximal to the superior pole of the patella and 1 finger breadth lateral to the lateral border of the patella.
    • Advance a needle through the skin, subcutaneous tissue, and lateral retinaculum into the suprapatellar pouch between the anterior femur and the quadriceps tendon from lateral to medial.
    • Aspirate the entire fluid collection.
      • When the syringe is full, clamp the hub of the needle with a sterile clamp.
      • Hold the hub and unscrew the syringe from the needle without removing the needle from the joint.
      • Apply a new syringe to the needle hub and continue aspirating.
      • Repeat these steps as many times as necessary to aspirate the effusion completely.
    • Remove the needle and apply a bandage.
    • Store the fluid for laboratory analysis (see Arthrocentesis chapter)
  • Pearls
    • A wide sterile skin preparation allows for manipulation of the knee and patella during aspiration.
    • Milking the effusion up into the suprapatellar pouch allows for a more complete aspiration of fluid.
    • Synovium can easily clog the needle tip during aspiration; use a large-bore needle (18-gauge or higher) to minimize this problem.
    • Injecting the skin with lidocaine at the injection/aspiration site is an option for patients concerned about pain.
      • It may allow the patient to tolerate the procedure better.
      • However, it does require an additional needle stick.
      • Alternatively, ethyl chloride sprayed on the skin immediately before the aspiration has a similar effect.
    • Never aspirate or inject through cellulitic skin.
  • Therapeutic injection:
    • Injection of corticosteroid:
      • Commonly performed after aspiration of synovial fluid that is not infected
      • The superolateral approach is the most reliable.
    • If an aspiration was performed:
      • Do not remove the needle from the joint.
      • Simply exchange the aspiration syringe with the syringe filled with the injectable and inject the medication without changing the needle’s location within the joint.
    • If an aspiration was not performed:
      • Identify the landmarks and insertion location as described for the superolateral approach into the suprapatellar pouch.
      • Advance the needle into the pouch.
      • Aspirate a small amount of synovial fluid to confirm intra-articular placement.
      • Once confirmed, inject the medication into the joint.
    • Remove the needle and apply a bandage.
  • Lidocaine:
    • Can be helpful in controlling pain caused by the injection.
    • Also can facilitate diagnostic procedures.
      • Painful knees are examined more easily after injection because of lidocaine’s numbing effect.
      • This effect is particularly helpful in determining the cause of a traumatic knee effusion.
      • Bupivicaine also may be used for a longer numbing effect.
      • On the day of injection, limit activity on the affected knee to activities of daily living.
  • Corticosteroid:
    • Can be useful for controlling pain and inflammation from noninfectious arthritis
    • Contraindicated if a septic knee has not been ruled out
    • A typical dose for the knee is 1 mL of kenalog (40 mg/mL), usually injected with 4 mL of 1% lidocaine.
    • Steroid medication usually takes 2-3 days to have an effect.
      • Manage the patient’s expectations by discussing this delayed pain relief at the time of the injection.
  • Hyaluronates are indicated for treatment of mild osteoarthritis.
Q: Which approach is least reliable in successfully injecting therapeutic agents into the knee joint?
A: The lateral joint line approach.
Q: Viscosupplementation therapy of the knee is indicated for which type of arthritis?
A: Osteoarthritis.

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