To develop and test the validity and reliability of a new instrument for measuring the thigh-foot angle (TFA) for the patients with in-toeing and out-toeing gait.

The new instrument (Thigh-Foot Supporter [TFS]) was developed by measuring the TFA during regular examination of the tibial torsional status. The study included 40 children who presented with in-toeing and out-toeing gaits. We took a picture of each case to measure photographic-TFA (P-TFA) in the proper position and to establish a criterion. Study participants were examined by three independent physicians (A, B, and C) who had one, three and ten years of experience in the field, respectively. Each examiner conducted a separate classical physical examination (CPE) of every participant using a gait goniometer followed by a TFA assessment of each pediatric patient with or without the TFS. Thirty minutes later, repeated in the same way was measured.

Less experienced examiner A showed significant differences between the TFA values depending on whether TFS used (left p=0.003 and right p=0.008). However, experienced examiners B and C did not show significant differences. Using TFS, less experienced examiner A showed a high validity and all examiner's inter-test and the inter-personal reliabilities increased.

TFS may increase validity and reliability in measuring tibial torsion in patients who has a rotational problem in lower extremities. It would be more useful in less experienced examiners.