Ankle joint movement:
The ankle joint allows three degrees of movement; therefore, it allows the foot to take up any position in space and adapt to any ground irregularities. The three main axes of the ankle joint complex are:
The transverse axis (green axis) that passes through the two malleoli and controls the movements of flexion (dorsiflexion) and extension (plantar flexion). Flexion refers to the movement when the foot's dorsum approximates the leg's anterior surface and vice versa for the extension.
The long axis lies parallel to the leg (red axis) and controls internal and external rotation movements. Internal rotation of the ankle refers to turning the big toe towards the body's midline and vice versa for external rotation.
The long axis that lies parallel to the foot (yellow axis) controls inversion and eversion. Inversion refers to the ankle movement allowing the sole facing towards the other leg and vice versa for eversion.
Sprained ankle injury mechanism:
A sprained ankle injury can happen in different directions and combinations of directions. Over 80% of the sprained ankle injuries resulted from an inversion sprain. One of the common ankle injuries occurs when the foot suddenly turns into inversion and extension (plantar flexion), which results from a sharp pain in the front and outside area of the ankle. Eversion sprained could also happen but less frequently due to the ankle's anatomy and the strong deltoid ligament.
During a sprained ankle injury, one or several ligaments may be damaged or completely torn depending on the accident's severity. The sprained ankle injury can be classified into three grades. The grading of the injury gives a guide to prognosis and helps determine the rate of rehabilitation.
Different injury mechanisms and severity may involve different ligaments; the most common affected ligament during inversion sprained is the anterior talofibular ligament. Let us take a look at what ligament(s) are involved in different injury mechanism and severity:
References
Kapandji, The Physiology of the Joint Volume 2 Lower Limb, Fifth Edition. Churchill Livingstone. Chapter 3.
Steven Roy, Richard Irvin. Sports Medicine Prevention, Evaluation, Management, and Rehabilitation. Prentice-Hall. Chapter 20.
Peter Brukner, Karim Khan. Clinical Sports Medicine. McGrawHill. Chapter 27.
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