Reliability of two instruments in the measurement of closed chain subtalar joint positions

Abnormal motion of the subtalar joint has often been implicated as a major contributing factor to lower limb pathology. However, the techniques used to assess this joint have not been adequately evaluated. The purpose of this study was to evaluate the inter- and intra-tester reliability of measuring neutral calcaneal stance position and resting calcaneal stance position using the gravity angle finder and a digital goniometer which has been specifically designed and manufactured by one of the authors. Two testers measured the neutral calcaneal stance position and resting calcaneal stance position of ten healthy volunteer participants (seven females, three males, mean age 21) using each device to establish both inter- and intra-tester reliability. The results indicated that inter- and intra-tester rearfoot measurement using both instruments had poor reliability (as evidenced by standard error of measurement values ranging from ± 3.7 to ± 8.5). Rearfoot measurement using the angle finder and a digital goniometer is unreliable and produces values with questionable clinical application. In light of such poor reliability, the validity of measuring frontal plane heel bisections to indicate subtalar joint position must also be seriously questioned.