Knee joint injection (technique)

Knee joint injections under image guidance ensure precise delivery of an injectate into the knee joint. Both fluoroscopy, ultrasound and CT can be used to guide and administer MRI and CT arthrogram injectate, or a steroid containing arthrogram injectate.

Indications

• MRI: retear of repaired meniscus
• CT: meniscal tear in those with MRI contra-indication
• anesthetic
  • pain - arthropathy i.e. osteoarthritis
  • diagnostic injection

Contra-indications

Absolute

• anaphylaxis to contrast/ injectate
• active local/ systemic infection 
• MRI contra-indication (MRI)

Relative

• bleeding diathesis
• non-arthrogram MRI not performed (MRI arthrogram)
• recent injection with steroid in same/other body parts (anesthetic arthrogram)
• unable to remain still for the procedure
• young age (anesthetic arthrogram)

Procedure

The general principles of knee arthrogram injections are to:

• cannulate the joint
• confirm an intra-articular position with imaging
• administer intra-articular injectate: the knee is the largest joint and the injectate volume should reflect this; at least 20 mL is injected in arthrograms, with 40 mL used in some institutions

Pre-procedural evaluation

Relevant imaging should be reviewed, and the details of the patient confirmed.  The patient should have an opportunity to discuss the risks and benefits and consent obtained.

Risks include:

• infection
• bleeding
• allergy 
• focal fat necrosis/skin discolouration at the injection site (anesthetic arthrogram)
• steroid flare (anesthetic arthrogram)

Equipment

• sterile probe cover (ultrasound)
• metal rod for marking and short connecting tube (fluoroscopy)
• biopsy grid and short connecting tube (CT)
• skin marker
• skin cleaning product
• sterile drape
• sterile field and tray for sharps
• syringe selection i.e. 10mL, 5mL and 20mL
• larger bore drawing up needle
• needle to administer local anesthetic i.e. 25-gauge needle
• needle to cannulate the joint i.e. 22 or 25-gauge needle
• injectants i.e. local anesthetics, iodinated contrast, corticosteroid preparation
• sterile gauze
• adhesive dressing

Syringe selection

A suggested syringe and injectate selection for a fluoroscopic-guided/CT guided MRI arthrogram injection:

• 5mL mL syringe: 5 mL of local anesthetic i.e. 1% lidocaine
• 10 mL syringe: 10mL non-ionic iodinated contrast i.e. iohexol 300
• 20mL syringe containing: 0.1 mL gadolinium, 9.9 ml 0.9% saline, 5 mL 0.5% ropivacaine, 5 mL Omnipaque 300

A suggested syringe and injectate selection for a fluoroscopic-guided/CT guided CT arthrogram injection:

• 5mL mL syringe: 5 mL of local anesthetic i.e. 1% lidocaine
• 10 mL syringe: 10mL non-ionic iodinated contrast i.e. iohexol 300
• 20mL syringe containing: 10 mL Omnipaque 300, 5 mL 0.9% saline, 5 mL 0.5% ropivacaine 

A suggested syringe and injectate selection for an ultrasound-guided knee anesthetic arthrogram injection:

• 5 mL syringe: 5 mL of local anesthetic i.e. 1% lidocaine
• 5mL syringe: 40mg triamcinolone acetonide (40 mg/1 mL) and 4 mL 0.5% ropivacaine

Needle selection

Smaller gauge needles can be less painful but are less stiff and can bend when trying to cannulate a joint. The needle should be long enough to reach the joint.

Knee: 22-gauge Quincke needle or 25-gauge needle

Technique

CT

• check for allergies and if on blood thinners
• consent
• optimize patient positioning, prone on the CT table, placing an overlying biopsy grid and perform planning CT scan
• identify needle entry point on planning images, mark the skin
• clean skin and draw up appropriate medications
• consider local anesthesia along the proposed needle path
• under CT guidance insert a needle into the targeted aspect of the joint
• confirm an intra-articular needle tip position with a small amount of iodinated contrast via tubing
• administer arthrogram injectate
• remove the needle and apply dressing/ band-aid as required

Fluoroscopy

Anterior approach

• check for allergies and if on blood thinners
• consent
• optimize patient positioning with the patient supine, knee in slight flexion, aiming for an anterior needle entry with the target knee closest to the practitioner
• optimize imaging field to include all of the knee joint, from above the patella to the tibial metaphysis 
• identify the central aspect of the lateral femoral condyle, 1cm caudal from the joint line, and using the metal rod, mark the skin at the target entry point
• clean skin and draw up appropriate medications
• consider local anesthesia along the proposed needle path
• under fluoroscopic guidance insert a needle parallel to the x-ray beam using an ‘eye of the needle approach’ into the targeted aspect of the joint until bone is reached
• confirm an intra-articular needle tip position with iodinated contrast via tubing and save a post-injection image
• administer arthrogram injectate
• remove the needle and apply dressing/ band-aid as required

Lateral subpatellar approach

• check for allergies and if on blood thinners
• consent
• optimize patient positioning with the patient supine, leg straight, aiming for a lateral to medial needle entry with the target knee closest to the practitioner
• optimize imaging field to include all of the knee joint, from above the patella to the tibial metaphysis 
• palpate the lateral aspect of the patella and confirm equator of the patella with fluoroscopy
• using the metal rod mark the skin at the target entry point, 1 cm inferior to the palpable line to allow for the patella depth
• clean skin and draw up appropriate medications
• consider local anesthesia along the proposed needle path
• under fluoroscopic guidance insert a needle, perpendicular to the x-ray beam, into the targeted aspect of the joint, aiming for the needle tip to reach the central point of the patella 
• confirm an intra-articular needle tip position with iodinated contrast via tubing and save a post-injection image
• administer arthrogram injectate
• remove the needle and apply dressing/ band-aid as required

Ultrasound

• check for allergies and if on blood thinners
• consent
• optimize patient positioning with the back of the bed at a slight incline, the patient supine, leg straight, aiming for a lateral to medial needle entry with the target knee closest to the practitioner
• using the US probe, identify the suprapatellar pouch under the quadriceps tendon in a transverse plane, optimize imaging focus and depth, and mark the targeted lateral skin entry point
• clean skin and draw up appropriate medications
• consider local anesthesia along the proposed needle path
• under ultrasound guidance insert the needle in-plane with the probe into the suprapatellar pouch
• administer arthrogram injectate under direct visualization
• remove the needle and apply dressing/ band-aid as required

Complications

Injecting a large volume during an arthrogram injection will cause an effusion and some knee stiffness, which will resolve over the next 24 hour period and the patient should be reassured this is normal post-procedure. In anesthetic injections, steroid flare is a relatively common side effect which will settle.  The most serious complication is infection causing septic arthritis. Steroid containing injections should be postponed if there are signs and/or symptoms of local and/ or systemic infection. Possible fat necrosis causing skin dimpling and skin discolouration can occur due to steroid leaking into the surrounding soft tissues , but less likely in deeper injections.

Siehe auch:

• Technik Gelenkinjektionen
• Arthrographie Kniegelenk