Patient Education and Consent
Prior to knee injection, informed consents must be obtained, and the physician should clearly explain to the patient the steps to be carried out, the expected benefits, and the risks and potential complications of the procedure. Patients are encouraged to ask questions and express understanding of the purpose and possible outcomes of the procedure.
Equipment
The use of ultrasonography (US) to guide intra-articular knee injections may improve accuracy and the likelihood of directing medication into the joint space.
A 22-gauge needle is ideal for knee injections with a 5-mL syringe, but any needle size from 22 to 25 gauge may be used. For injections, needle gauge should be based on medication viscosity. A higher-gauge needle may increase the resistance in pushing the medication while minimizing discomfort. For arthrocentesis, a smaller-gauge needle (eg, 18-22 gauge) is preferred. Syringe size should be based on the same principles as mentioned above. (See the images below.)
For sterilization, either iodine or hexachlorodine scrub should be used. For anesthesia, a bleb or lidocaine or an ethyl chloride spray should be used.
In obese patients, it is better to perform the knee injection under fluoroscopic guidance.
Patient Preparation
Careful initial palpation and marking of the injection site may reduce the need to repalpate an already prepared site. During the initial marking of the intra-articular injection target site, the knee should be flexed 90° to expose the joint space for the anteromedial or anterolateral approach and almost fully or fully extended for the superolateral or superomedial approach. The selected skin site for injection can be marked. Sterile gloves may be used.
Using sterile techniques, skin over the target area may be prepared with iodine disinfectant × 3, allowed to air-dry, and then wiped with alcohol prior to needle placement; alternatively, cyclohexidine may be used for skin preparation in place of iodine plus alcohol.
Any number of the relatively insoluble injectable corticosteroids, including triamcinolone acetonide 10-40 mg, triamcinolone hexacetonide 10-40 mg, or prednisolone acetate 10-25 mg, or slightly soluble corticosteroids, such as methylprednisolone acetate 40-80 mg or triamcinolone diacetate 20-40 mg, may be used. [9, 8]
Anesthesia
A 10- to 15-s stream of ethyl chloride topical anesthetic spray can be steadily directed at the skin area over the target injection site prior to needle advancement. Lidocaine 1-2% can be injected over the target site via a 25-gauge 1.5-in. (3.8-cm) needle after negative aspiration for further numbing effect prior to the steroid injection, or it can be injected directly into the knee joint as a mixture with corticosteroid.
Positioning
For the anterolateral or anteromedial approach, the patient can be in the sitting or supine position, with the knee flexed to 90° to allow easy access to the joint capsule. Knee radiography would show if medial or lateral joint-space narrowing predominates.
For the superolateral or superomedial approach, the knee is almost fully or is fully extended to allow gentle rocking of the patella. The needle is directed under the proximal patella near and parallel to the undersurface of the quadriceps tendon insertion on the patella. [9, 8]
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Sterile glove
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Sterile 25-Gauge x 1.5-inch needle
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Anteromedial approach to intra-articular knee joint injection with patient in sitting position and knee flexed 90 degrees (ThePainSource.com)
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Anteromedial approach to intra-articular knee joint injection with patient in sitting position and knee flexed 90 degrees (ThePainSource.com)
Tables
Agent |
Relative Anti-inflammatory Potency |
Relative Mineralocorticoid Potency |
Solubility |
Hydrocortisone |
1 |
2-3 |
High |
Prednisolone |
4 |
1 |
Medium |
Methylprednisolone |
5 |
0 |
Medium |
Triamcinolone |
5 |
0 |
Medium |
Betamethasone |
20-30 |
0 |
Low |
Dexamethasone |
20-30 |
0 |
Low |
