Standardized Knee Ultrasound Protocol for Dynamic Meniscus Extrusion Evaluation After Meniscus Allograft Transplantation

Abstract

Meniscus allograft transplantation has demonstrated promising clinical outcomes in the management of total meniscal deficiency. Magnetic resonance imaging (MRI) is commonly used to assess graft integrity and position, particularly meniscus extrusion; however, MRI has limitations, including high cost, limited accessibility, and inability to provide dynamic, real-time assessments. Furthermore, static MRI findings often show poor correlation with clinical outcomes, underscoring the need for complementary methods. This Technical Note presents a standardized knee ultrasound protocol for dynamic evaluation of meniscus extrusion after meniscus allograft transplantation. Ultrasonography provides a cost-effective, accessible, and in-office modality that enables real-time assessment of graft function under axial loading, offering a valuable alternative to MRI for postoperative monitoring.

Fig 1

Clinical assessment of the right knee in the supine position. (A) With the patient lying supine and the right knee in in midflexion, palpation of the MCL and the joint line (star) is performed. (B) While maintaining palpated MCL and joint space position (star), the knee is extended fully. (MCL, medial collateral ligament.)

Fig 2

Low-focus ultrasound overview of the medial compartment of the right knee. With the patient supine and the transducer placed medially, the low-focused, high-resolution ultrasound scan shows the MCL (yellow), femoral and tibial cortex margin (light blue), and the meniscus allograft (green). (MCL, medial collateral ligament.)

Fig 3

High-focused ultrasound transducer placement in supine position. After obtaining a less-focused overview with a linear transducer, the optimal imaging location on the medial side of the right knee is marked. A high-focused, high-resolution transducer (star) is then placed on the exact mark to optimize visualization.

Fig 4

High-resolution ultrasound image of the medial compartment of the right knee in supine position. Using a high-focused, high-resolution transducer visualization of the MCL (yellow), femoral and tibial cortex margin (blue), osteophytes (red), and meniscus allograft (green) is achieved. (MCL, medial collateral ligament.)

Fig 5

Standing-position high-resolution ultrasound transducer placement. With the patient standing, the high-focused, high-resolution transducer (star) is positioned identically to the supine scan, aligned with the pre-marked location on the medial right knee.

Fig 6

Meniscal extrusion measurement technique on high-resolution ultrasound. On a medial ultrasound image of the right knee, 2 parallel reference lines are drawn: one along the joint line (blue), connecting the femoral and tibial cortex margins, and a second along the outer margin of the meniscal allograft (yellow). A perpendicular line (red) connecting these 2 is used to quantify meniscal extrusion.

Fig 7

Meniscus extrusion measurement with exclusion of osteophytes in a medial right knee ultrasound. With the patient supine and the transducer placed medially, meniscus extrusion is measured as the perpendicular distance (green) between the joint line (blue) and the outer meniscal border (yellow). Osteophytes (red) are excluded.