Skill Checkup: Knee Injection

Dean H. Hommer, MD

Disclosures

October 28, 2019

Knee pain and stiffness can be debilitating and difficult to treat. Lifestyle-limiting knee conditions may negatively affect body image and emotional well-being. Weight management, exercise/strengthening programs, physical therapy, physical modalities, orthotics, medications, intra-articular knee injections, and surgery are some of the approaches used to treat knee pain.

The most common type of intra-articular knee injection is with corticosteroids, but other agents used include infliximab, hyaluronic acid, botulinum neurotoxin, and platelet-rich plasma (PRP).

Indications 

Steroid injections have been shown to relieve pain and inflammation in individuals with osteoarthritis (including osteoarthritis complicated by Baker cysts), juvenile idiopathic arthritis, psoriatic arthritis, acute monoarticular gout, pseudogout, and rheumatoid arthritic knees.

Intra-articular infliximab can be used to treat refractory knee monoarthritis/synovitis in patients with rheumatoid arthritis, Behçet disease, and spondyloarthropathy (eg, ankylosing spondylitis) that is resistant to systemic treatment.

Intra-articular knee injections of hyaluronic acid have been shown to provide functional and perceived benefits in knee osteoarthritis. Such injections have also been shown to be helpful in patients with knees that are both rheumatoid arthritic and osteoarthritic.

Intra-articular injection of botulinum neurotoxin A into the knee joint may provide therapeutic pain relief in patients with advanced knee osteoarthritis.

Intra-articular knee injections of homologous PRP have been shown to improve function and quality of life in patients with degenerative lesions of the knee cartilage and osteoarthritis at 6 months post-injection.

Procedure

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 x 3, allowed to air-dry, and then wiped with alcohol prior to needle placement; alternatively, chlorhexidine 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.

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 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.

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 whether 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.

The best approach to a knee injection is the path of least obstruction and maximal access to the synovial cavity, which could be superolateral, superomedial, or anteromedial/anterolateral.

Superolateral approach

For the superolateral approach, the patient lies supine with the knee almost fully or fully extended, with a thin pad support underneath the knee to facilitate relaxation. The clinician's thumb is used to gently rock and then stabilize the patella while the needle is inserted underneath the superolateral surface of the patella, aimed toward the center of the patella, and then directed slightly posteriorly and inferomedially into the knee joint.

Superomedial approach

For the superomedial approach, the patient lies supine with the knee almost fully or fully extended, with a thin pad support underneath the knee to facilitate relaxation. The clinician's thumb is used to gently rock and then stabilize the patella while the needle is inserted underneath the superomedial surface of patella, aimed toward the center of the patella, and then directed slightly posteriorly and inferolaterally into the knee joint.

Anterolateral and anteromedial approaches

For the anterolateral and anteromedial approaches, the patient can sit or lie supine with the knee flexed 90° to afford better exposure of the intra-articular surface and thus facilitate ease of needle entry into the joint space.

The sterile needle is inserted either lateral to the patellar tendon (for the anterolateral approach) or medial to the tendon (for the anteromedial approach), approximately 1 cm above the tibial plateau, and directed 15°-45° from the anterior knee surface vertical midline toward the intra-articular joint space.

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