Experimental Comparison of the Clinical Measurement of Ankle Joint Dorsiflexion and Radiographic Tibiotalar Position

Clinical measurement of ankle dorsiflexion is typically used to diagnose limited ankle range of motion. Controversy and a lack of clarity continue regarding the most accurate clinical method of measuring ankle joint dorsiflexion and the effect that the foot position (supinated, neutral, pronated) has on the true tibiotalar position. We investigated the effects of supinated, neutral and pronated foot positions on the clinical dorsiflexion measurements in 50 healthy subjects and compared these results to the radiographic measurement of tibiotalar joint position with the ankle maximally dorsiflexed in each of the 3 foot positions. Interrater reliability was confirmed to be adequate among the 3 clinicians of varied skill levels. Radiographic measurements of the tibiotalar position showed very little change in each of the 3 foot positions, with a total difference of 0.35° between supination and pronation. However, we found a mean difference of 14° of dorsiflexion in the clinical measurements between the pronated and supinated foot position, with a 9.08° difference between the neutral and supinated positions. Motion of the foot between the neutral and supinated positions introduced an additional source of potential error from the measurement technique when using the neutral position as the standard, which has been recommended in the past. We recommend a supinated foot position as a more reliable foot position for measuring the clinical ankle joint range of motion and propose it as a potential standard.