Knee injection technique

The knee injection technique is a common treatment option for various conditions, including osteoarthritis, rheumatoid arthritis, and knee injuries. These injections can help relieve pain and inflammation, and in some cases, may even delay the need for surgery.

Relevant Anatomy

In an average-sized adult, the knee joint has a potential capacity of approximately 120 ml or more. The joint capsule is lined with synovium, which is folded and therefore has a large surface area. Because of this, a larger knee requires more volume to fully cover the target area. Plicae (synovial folds) may be present within the joint and can also become inflamed. The suprapatellar bursa is a continuation of the synovial capsule, and there are numerous other bursae surrounding the joint.

Required Equipment

Knee Injection Techniques

Several approaches have been described for accessing the intra-articular space for knee injections, including superolateral, superomedial, inferolateral, and inferomedial. The superolateral approach has been shown to be the most accurate and reproducible method, with a 93% accuracy rate compared to 71–75% for the inferomedial and inferolateral approaches.

Superolateral Approach

The superolateral knee injection technique can be performed step-by-step as follows:

• Place the patient in a supine position with the knee fully extended.
• Examine the knee to estimate the approximate amount of joint fluid present (this determines the size of the syringe used for aspiration) and check for signs of overlying cellulitis (avoid inserting the needle through an area of potential infection).
• Palpate the superolateral part of the patella and mark the skin one finger’s width above and one finger’s width lateral to this point as the starting site.
• Prepare the skin in this area with alcohol and povidone-iodine.
• Put on sterile gloves.
• Use your non-dominant hand to gently tilt the patella, which increases the available space and makes it easier to insert the needle into the intra-articular space.
• Direct the needle 45° distally and 45° posteriorly into the intra-articular space, being careful not to touch the articular surfaces of the patella or the corresponding trochlea.
• Once in the intra-articular space, begin injecting the prepared medication.
• After the injection, remove the needle from the knee. Clean the prepared skin with an alcohol swab, dry it with a gauze swab, and apply a bandage.

Inferolateral Approach

The inferolateral knee injection technique can be performed step-by-step as follows:

• Position the patient in a seated position with the knee bent at 90° over the end of the examination table.
• Palpate the lower pole of the patella, the lateral part of the patellar tendon, and the proximal part of the lateral tibial plateau. A palpable "soft spot" should be present one finger’s width proximal to the lateral tibial plateau, directly lateral to the lateral side of the patellar tendon. Mark this location as the starting point for aspiration/injection.
• Prepare the skin in this area with alcohol and povidone-iodine.
• Put on sterile gloves.
• Direct the needle from the soft spot starting point approximately 30° medially toward the intercondylar notch, taking care not to touch the articular surface of the femoral condyle.
• Once the needle is in the intra-articular space, begin injecting the prepared medication.
• After the injection, remove the needle from the knee. Clean the prepared skin with an alcohol swab, dry it with a gauze swab, and apply a bandage.

After a knee injection, avoid excessive strain until symptoms subside, then begin strengthening and mobilization exercises. One study found that complete bed rest for 24 hours after the injection led to better outcomes in rheumatoid knees; however, this bed rest required hospitalization, which is not cost-effective.

Notes

In obese patients, using a longer needle and a larger volume of 40 mg Adcortyl can bathe a greater portion of the joint surface. Hyaluronan injections can be administered, but they are more expensive than corticosteroid injections and do not appear to provide longer-lasting benefits.

A knee injection provides pain relief of variable duration, but this can last longer if the knee is not overused. Repeat injections can be given at intervals of at least 3 months, with an annual X-ray to monitor joint degeneration. If the patient is awaiting surgery, discuss this with the surgeon before proceeding.

References and Further Reading

1. Injection Techniques in Musculoskeletal Medicine. A Practical Manual for Clinicians in Primary and Secondary Care. Fifth Edition.
2. Orthopedic Procedures in the Emergency Department: An Illustrative Guide for the House Officer by Eric J. Strauss and Kenneth A. Egol.
3. Chernchujit B, Tharakulphan S, Apivatgaroon A, Prasetia R. Accuracy comparisons of intra-articular knee injection between the new modified anterolateral approach and the superolateral approach in patients with symptomatic knee osteoarthritis without effusion. Asia Pac J Sports Med Arthrosc Rehabil Technol. 2019 Mar 26;17:1-4. doi: 10.1016/j.asmart.2019.02.001. PMID: 30976521; PMCID: PMC6438910.
4. Fusco G, Gambaro FM, Di Matteo B, Kon E. Injections in the osteoarthritic knee: a review of current treatment options. EFORT Open Rev. 2021 Jun 28;6(6):501-509. doi: 10.1302/2058-5241.6.210026. PMID: 34267940; PMCID: PMC8246115.
5. Testa G, Giardina SMC, Culmone A, Vescio A, Turchetta M, Cannavò S, Pavone V. Intra-Articular Injections in Knee Osteoarthritis: A Review of Literature. J Funct Morphol Kinesiol. 2021 Feb 3;6(1):15. doi: 10.3390/jfmk6010015. PMID: 33546408; PMCID: PMC7931012.