Adult-acquired flatfoot deformity and age-related differences in foot and ankle kinematics during the single-limb heel-rise test.

STUDY DESIGN: Cross-sectional laboratory study.

OBJECTIVE: To compare single-limb heel-rise performance and foot-ankle kinematics between persons with stage 2 adult-acquired flat foot deformity (AAFD) and healthy controls.

BACKGROUND: The inability to perform a single-limb heel rise is considered a positive functional diagnostic test for AAFD. However, which foot motions contribute to poor performance of this task are not known.

METHODS: Fifty individuals participated in this study, 20 with stage 2 AAFD (mean ± SD age, 57.6 ± 11.3 years), and 15 older participants (age, 56.8 ± 5.3 years) and 15 younger participants (age, 22.2 ± 2.4 years) without AAFD as control groups. Forefoot (sagittal plane) and rear foot (sagittal and frontal planes) kinematics were collected using a 3-D motion analysis system. Heel-rise performance (heel height) and kinematics (joint angles, excursions) were evaluated. One-way and 2-way analyses of variance were used to examine differences in heel-rise performance and kinematics between groups.

RESULTS: Individuals with AAFD and older controls demonstrated lower heel-rise height than those in the younger control group (P<.001). Persons with AAFD demonstrated higher degrees of first metatarsal dorsiflexion (P<.001), lower ankle plantar flexion (P<.001), and higher subtalar eversion (P = .027) than those in the older control group. Persons with AAFD demonstrated lower ankle excursion (P<.001) and first metatarsal excursion (P<.001) than those in the older control group, but no difference in subtalar excursion (P = .771).

CONCLUSION: Persons with stage 2 AAFD did not achieve sufficient heel height during a single-leg heel rise. Both forefoot and rear foot kinematics in the sagittal plane, as opposed to the frontal plane, contributed to the lower heel height in participants with stage 2 AAFD. Older controls demonstrated lower heel-rise height than younger controls, indicating that clinical expectations of heel-rise performance may need to be adjusted for age.