Mechanical stability, muscle strength and proprioception in the functionally unstable ankle

Area of Science:

• Orthopedics
• Sports Medicine
• Biomechanics

Background:

• Functional ankle instability is a frequent complication of inversion sprains.
• Potential causes include talocrural joint mechanical instability, peroneal muscle weakness, and motor incoordination from impaired proprioception.

Purpose of the Study:

• To document physical examination findings in functionally unstable ankles.
• To evaluate the relevance of mechanical stability, muscle strength, and proprioception theories.

Main Methods:

• Physical examination of 45 subjects with unilateral functional ankle instability.
• Assessment of mechanical stability using standard clinical tests.
• Measurement of evertor and inventor muscle strength via Cybex II dynamometer.
• Evaluation of dynamic ankle control and proprioception using the Uni-axial Balance Evaluator (UBE).

Main Results:

• Mechanical instability was often absent in functionally unstable ankles.
• Evertor muscle strength did not differ between normal and unstable ankles.
• UBE results suggested impaired proprioception contributes to functional instability.

Conclusions:

• Impaired proprioception is a likely factor in functional ankle instability.
• Mechanical instability and peroneal muscle weakness may not be primary contributors.
• Further research is recommended to fully elucidate the causes of functional ankle instability.