Ultrasound Imaging of the Articularis Genus Muscle: Implications for Ultrasound-Guided Suprapatellar Recess Injection

Abstract

Elucidating its dynamic interaction within the knee joint, this exploration delves into the awareness regarding the articularis genus muscle for ultrasound-guided suprapatellar recess injections. While injections into the infrapatellar recess may proceed without ultrasound guidance, we highlight concerns regarding the potential cartilage injury. In contrast, especially with ultrasound guidance, suprapatellar recess injections significantly mitigate this risk, especially in the case of collapsed recess. Originating from the distal femur and vastus intermedius, the articularis genus muscle influences the tension of the suprapatellar recess during knee motion. Sonographically identifying this muscle involves visualizing the slender linear structure of the suprapatellar recess, with guidance on differentiation from the vastus intermedius. We provide a succinct approach to ultrasound-guided suprapatellar recess injections, emphasizing needle insertion techniques and strategies to prevent fluid accumulation. In conclusion, this study serves as a concise clinician's guide, underscoring the significance of the articularis genus muscle's sonoanatomy in ultrasound-guided suprapatellar recess injections. Ultimately, procedural precision and patient safety can be advanced in this aspect.

Keywords: hyaluronic acid; knee; pain; quadriceps; ultrasonography.

Figure 1

During knee flexion when the articularis genus (orange striated lines) and quadriceps (green striated line) remain inactive, reduced tension is exerted on the wall of the suprapatellar recess (white striated lines). This diminished tension causes the recess to collapse, resulting in a slender appearance (A). Conversely, with knee extension and the activation of the articularis genus, the tension on the wall of the suprapatellar recess intensifies. This increased tension leads to the dilation of the suprapatellar recess (B).

Figure 2

Cadaveric dissection images depict the articularis genus muscle (arrowheads) in different cases (A,B). Arrow, the existing portal of the suprapatellar recess. QT, quadriceps tendon; VI, vastus intermedius muscle; VM, vastus medialis muscle; FE, femur; FP, fat pad; and P, patella.

Figure 3

Cadaveric histology dissection images illustrate the articularis genus (AG) muscle in different cases (A,B). P, patella; FE, femur; T, tibia; QT, quadriceps tendon; VI, vastus intermedius; and stars, fat tissue.

Figure 4

T1-weighted axial (A) and sagittal (B) views of magnetic resonance imaging for the articularis genus muscle. Stars, fat tissue.

Figure 5

Sagittal ultrasound imaging and schematic drawing of the articularis genus (AG) muscle at the suprapatellar region during neutral knee extension (A) and maximal knee extension (B). Black arrows, aponeurosis from the rectus femoris; white arrowheads, aponeurosis from the vastus lateralis and medialis; white arrows, aponeurosis from the vastus intermedius; stars, fat tissue; asterisk, suprapatellar recess; FE, femur; P, patella; and SF, suprapatellar fat pad; red square, transducer’s location.

Figure 6

Sagittal ultrasound imaging and schematic drawing of the articularis genus (AG) muscle at the distal femoral region during neutral knee extension (A) and maximal knee extension (B), facilitating the visualization of vastus intermedius muscle (VI). Black arrows, aponeurosis from the rectus femoris; white arrowheads, aponeurosis from the vastus lateralis and medialis; white arrows, aponeurosis from the vastus intermedius; stars, fat tissue; asterisks, suprapatellar recess; FE, femur; RF, rectus femoris; red square, transducer’s location.

Figure 7

Axial ultrasound imaging and schematic drawing of the articularis genus (AG) muscle at the proximal femoral (A) and suprapatellar (B) regions. Black arrows, aponeurosis from the rectus femoris; white arrowheads, aponeurosis from the vastus lateralis and medialis; white arrows, aponeurosis from the vastus intermedius; star, fat tissue; asterisk, suprapatellar recess; FE, femur; P, patella; VI, vastus intermedius muscle; VM, vastus medialis muscle; VL, vastus lateralis muscle; red and blue squares, transducer’s location.

Figure 8

Ultrasound imaging and schematic drawing for the guided injection of the suprapatellar recess before (A) and after (B) introducing the injectate. Black arrows, aponeurosis from the rectus femoris; white arrowheads, aponeurosis from the vastus lateralis and medialis; white arrows, aponeurosis from the vastus intermedius; asterisk, suprapatellar recess; FE, femur; VM, vastus medialis muscle; VL, vastus lateralis muscle; AG, articularis genus muscle; red square, transducer’s location.