[Rotational Laxity of the Knee Joint - In Vivo MRI Study]

Area of Science:

• Orthopedics
• Biomechanics
• Knee Kinematics

Background:

• Understanding knee joint mechanics is crucial for diagnosing and treating knee pathologies.
• Tibiofemoral rotation plays a significant role in overall knee function and stability.

Purpose of the Study:

• To evaluate tibiofemoral rotation during simulated squatting.
• To investigate the relationship between femur position in full extension and its rotation during knee flexion.

Main Methods:

• Utilized 2D MRI measurements on 10 healthy volunteers with fixed feet and ankles.
• Employed a mathematical model to simulate femur rotation during flexion from full extension to 90°.

Main Results:

• In full extension, the femur exhibited an average of 12.8° internal rotation relative to the tibia.
• During 90° flexion, the femur demonstrated an average of 12.2° external rotation, maintaining the femoral head within the acetabulum.

Conclusions:

• Knee flexion necessitates coupled external rotation of the femur on a rotationally fixed tibia to ensure acetabular containment.
• This obligatory rotation is influenced by the initial rotational position of the femur and the anatomical congruity of the knee joint.