Weight-bearing ankle dorsiflexion range of motion-can side-to-side symmetry be assumed?

Context: In clinical practice, the range of motion (ROM) of the noninvolved side often serves as the reference for comparison with the injured side. Previous investigations of non-weight-bearing (NWB) ankle dorsiflexion (DF) ROM measurements have indicated bilateral symmetry for the most part. Less is known about ankle DF measured under weight-bearing (WB) conditions. Because WB and NWB ankle DF are not strongly correlated, there is a need to determine whether WB ankle DF is also symmetrical in a healthy population. Objective: To determine whether WB ankle DF is bilaterally symmetrical. A secondary goal was to further explore the correlation between WB and NWB ankle DF ROM. Design: Cross-sectional study. Setting: Training facility of the Israeli Defense Forces. Patients or Other Participants: A total of 64 healthy males (age = 19.6 ± 1.0 years, height = 175.0 ± 6.4 cm, and body mass = 71.4 ± 7.7 kg). Main Outcome Measure(s): Dorsiflexion ROM in WB was measured with an inclinometer and DF ROM in NWB was measured with a universal goniometer. All measurements were taken bilaterally by a single examiner. Results: Weight-bearing ankle DF was greater on the nondominant side compared with the dominant side (P <.001). Non-weight-bearing ankle DF was not different between sides (P =.64). The correlation between WB and NWB DF was moderate, with the NWB DF measurement accounting for 30% to 37% of the variance of the WB measurement. Conclusions: Weight-bearing ankle DF ROM should not be assumed to be bilaterally symmetrical. These findings suggest that side-to-side differences in WB DF may need to be interpreted while considering which side is dominant. The difference in bilateral symmetry between the WB and NWB measurements, as well as the only moderate level of correlation between them, suggests that both measurements should be performed routinely.