A 68 year old female with no significant past medical history presents to the Emergency Department (ED) with one day of right knee pain after falling off her bicycle onto her right side. She was immediately unable to bear weight on her right leg.
Vitals: T 98.3, HR 73, RR 18, BP 114/70, SpO2 99%
Right leg exam: mild right knee effusion. No ligamentous laxity. Tenderness to palpation over lateral joint line > medial joint line. Tenderness to palpation over proximal anterior tibia. Knee extension limited due to pain. Neurovascularly intact with soft compartments.
Radiographic imaging demonstrated an isolated right tibial plateau fracture depression of the lateral plateau. The patient reports she is in severe pain but dislikes taking both over-the-counter and opioid pain medications.
What nerves may be targeted to provide pain relief to her knee while maintaining motor function? What anatomic landmarks should be used on ultrasound to identify the branches of this nerve?
Answer and Learning Points
The genicular nerves derive from various major lower extremity nerve branches (femoral, obturator, sciatic, tibial) nerves and provide sensation to the knee capsule and joint. Cadaveric studies suggest that most genicular nerves are easily identifiable landmarks that may be used for therapeutic purposes. 5 Genicular nerve blocks (GNB) are traditionally used in this setting of chronic osteoarthritis knee pain via radiofrequency ablation or perioperative knee pain via ultrasound (1-4, 9).
The use of a GNBs in the ED is a novel technique to provide motor-sparing, pain relief for acute knee pain. This 68 year old patient with an isolated lateral tibial plateau fracture reported 4/10 pain over her proximal tibia at rest and 8/10 over her proximal tibia with movement. Written informed consent was obtained for GNBs of her right knee. Anatomic landmarks for the superior lateral (Image A,B) , superior medial (Image C,D), and inferior medial (Image D,E,F) genicular nerves were identified on ultrasound.
The ultrasound probe was placed in the sagittal orientation for each site. The superior lateral genicular nerve was located on ultrasound at the junction of the lateral femoral epicondyle and the epiphysis of the shaft of the femur, adjacent to the superior lateral genicular artery (Image A,B). The superior medial genicular nerve (SMGN) can be identified on ultrasound at the junction of the medial femoral epicondyle and the epiphysis of the shaft of the femur, adjacent to the superior medial genicular artery (Image C, D). The inferior medial genicular nerve (IMGN) can be identified on ultrasound at the junction of the medial tibial epicondyle and the epiphysis of the shaft of the tibia, adjacent to the inferior medial genicular artery (Image E, F, G) (6-8).
Under ultrasound guidance and using sterile technique, the skin was first anesthetized with 1% lidocaine after each site. A 21-gauge, 2 inch echogenic needle was inserted percutaneously and advanced under ultrasound guidance using an out-of-plate technique to inject 1.5 mL of 0.5% bupivacaine around the right superior lateral, superior medial, and inferior medial genicular nerves.
- Genicular nerves derive from several lower extremity nerves and supply sensory innervation to the knee.
- The superior lateral, superior medial, and inferior medial genicular nerves are commonly targeted for pain relief with chronic knee osteoarthritis and postoperative pain.
- The SLGN, SMGN, IMGN are easily located on ultrasound using anatomic landmarks (junction between epicondyles and epiphysis of the femur and tibia, adjacent to paired genicular arteries).
- To obtain the images, you can use the linear probe in the sagittal location over lateral femoral epicondyle, medial femoral epicondyle, and medial tibial epicondyle.
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This post was written by Julia Sobel MD, with editing from Jessica Oswald MD, Charles Murchison MD and Amir Aminlari MD.