What is the evaluation for functional instability in patients with ankle sprains?

Updated: Jan 14, 2019
  • Author: Craig C Young, MD; Chief Editor: Sherwin SW Ho, MD  more...
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Functional instability of the ankle has been defined variously as the occurrence of frequent sprains, difficulty running on uneven surfaces, difficulty cutting or jumping, and recurrent giving-way for at least 6 months despite adequate nonsurgical therapy. [38] Instability may result from tibiotalar laxity or subtalar instability.

Patients with subtalar instability may report giving-way symptoms of the foot during activity and a history of recurrent instability, pain, swelling, and stiffness. The symptoms are often vague, and distinguishing between subtalar and tibiotalar instability is difficult. Patients may also have pain over the sinus tarsi or deep pain in the subtalar area.

This sinus tarsi syndrome can be a component of subtalar instability, with tenderness to palpation over the sinus tarsi and pain upon forced inversion of the foot. Increased internal rotation of the calcaneus is also a common finding, and excessive distal displacement of the calcaneus may occur in relation to the talus compared with the normal side. Subtalar instability should be regarded as contributing to the patient's symptoms, especially in a high-energy injury.

Chronic medial ligament instability is uncommon, but it produces discomfort on the medial side of the ankle and is associated with slight valgus and abduction of the ankle with each step.

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