Ligamentous or joint laxity is a clinical entity characterized by increased joint mobility beyond the range of motion regarded as normal, and joint mobility is an effective indicator of the degree of laxity. We examined the influence of ligamentous laxity on the range of ankle dorsiflexion with the knee flexed and extended, comparing lax adults with a control (nonlax) group.
The sample comprised 400 individuals: 200 in the control group (mean ± SD age, 32.49 ± 11.06 years) and 200 in the lax group (mean ± SD age, 29.82 ± 9.40 years). The Beighton criteria were applied to each participant to diagnose laxity or nonlaxity, and sex, age, and angle range of bilateral dorsiflexion with the knee extended and flexed were recorded.
The mean ± SD dorsiflexion range with the knee straight was 16.14° ± 5.29° left ankle and 21.21° ± 4.93° right ankle in the lax group and 12.94° ± 4.17° left ankle and 17.08° ± 4.40° right ankle in the control group. The respective values with the knee flexed were 15.84° ± 5.31° and 21.21° ± 4.80° in the lax group and 12.95° ± 3.95 and 17.23° ± 4.25° in the control group.
In this sample, ankle dorsiflexion range in the lax group was 4° bigger than that in the control group in both knee positions.