The external rotation stress test helps in diagnosing syndesmotic injuries. The knee is flexed 90 degrees and the ankle is in neutral. Stabilizing the tibia and fibula with one hand, the examiner externally rotates the ankle with the other. Widening of the syndesmosis indicates a positive test.
Beumer et al tested the squeeze, fibula translation, Cotton, and external rotation tests. None of the syndesmotic tests was uniformly positive in chronic syndesmotic injury. The external rotation test had the fewest false-positive results, the fibula translation test the most. The external rotation test had the smallest inter-observer variance.
The video is an example of the Cotton test for evaluation of syndesmotic instability.
Beumer A, Swierstra BA, Mulder PG: Clinical diagnosis of syndesmotic ankle instability: Evaluation of stress tests behind the curtains. Acta Orthop Scand 2002;73:667-669.
PMID:12553515 (Link to Abstract)
Boytim MJ, Fischer DA, Neumann L: Syndesmotic ankle sprains. Am J Sports Med 1991;19:294-298.
PMID:1907807 (Link to Abstract)