Frontal plane ankle stiffness increases with weight-bearing

Area of Science:

• Biomechanics
• Musculoskeletal Injury Research
• Orthopedics

Background:

• Ankle sprains are common, with 30-40% leading to chronic instability.
• Current assessments of ankle stability are often unloaded, questioning their clinical relevance.
• Ankle impedance quantifies stability, but frontal plane and weight-bearing effects are understudied.

Purpose of the Study:

• To investigate the effect of weight-bearing on frontal plane ankle impedance.
• To determine if joint loading and muscle activation influence ankle stability during weight-bearing.

Main Methods:

• Subjects systematically altered weight on the ankle.
• Imposed frontal plane rotations were applied to estimate ankle impedance.
• Ankle stiffness was measured under varying weight-bearing conditions.

Main Results:

• Ankle stiffness increased proportionally with applied weight.
• Increased joint loading and muscle activation contributed to higher stiffness.
• Men exhibited greater ankle stiffness than women across most weight-bearing levels.

Conclusions:

• Weight-bearing conditions significantly impact frontal plane ankle impedance.
• Clinical assessment of ankle stability should incorporate weight-bearing.
• This approach may improve evaluation of chronic ankle instability and sprain risk prediction.