Instability of the subtalar joint. Diagnosis by stress tomography in three cases.

Lateral instability in the subtalar joint was documented by a method of stress tomography in three patients. The subtalar inversion angle averaged 38 degrees +/- S.D. 6 degrees in asymptomatic feet and 57 degrees +/- S.D. 5 degrees in those with unstable subtalar joints . Review of the literature suggests that as many as 10 per cent of patients having the Watson-Jones procedure for abnormal talar tilt also have instability in the subtalar joint. It is felt that the subtalar joint should be evaluated in patients seen with the clinical symptom of lateral instability.