Physiologic Medial Meniscal Extrusion With Loading and Flexion Detected by Ultrasound

Area of Science:

• Orthopedics
• Radiology
• Biomechanics

Background:

• Medial meniscal extrusion (MME) is a risk factor for knee osteoarthritis.
• Current ultrasound protocols for MME vary in flexion angles and weightbearing, complicating interpretation.
• Understanding MME's response to loading and position is crucial.

Purpose of the Study:

• To investigate the influence of loading and knee flexion on medial meniscal extrusion (MME) using ultrasound.
• To compare MME across different stances (supine, single-leg, double-leg) and flexion angles (neutral, 20°, 45°).

Main Methods:

• Descriptive laboratory study involving 21 asymptomatic volunteers.
• Ultrasound imaging of the medial meniscus in coronal plane.
• Real-time knee angles measured with motion capture during supine and weightbearing positions at varying flexion angles.

Main Results:

• MME was significantly lower in supine (1.1) compared to single-leg (1.3) and double-leg (1.3) stances (P < .0001).
• Increasing knee flexion significantly reduced MME, with the lowest extrusion at 45° (1.0) compared to neutral (1.4) (P < .0001).
• No significant difference in MME was found between right and left legs.

Conclusions:

• Unloaded, supine ultrasound examinations of MME may have limited clinical value.
• Loaded ultrasound assessments better represent meniscal biomechanics during activities of daily living.
• Assessing physiologic meniscal behavior aids in managing meniscal pathology.