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.