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Simulated Ankle Equinus Affects Knee Kinematics During Gait



It is critical to distinguish gait compensations from true abnormalities when planning interventions to improve gait in individuals with neuromuscular disorders.


The aim of this study was to determine the effect of isolated ankle equinus on knee kinematics during the initial contact phase of gait.


Ten healthy subjects (29 + 4.3 years) participated, and testing occurred in a motion analysis laboratory. This cross-sectional study investigated five gait conditions in each subject: shoe alone, shoe with unilateral ankle foot orthosis locked at neutral, 10°, 20°, and 30° of fixed ankle plantar flexion. Gait kinematics were recorded and calculated with 3D motion analysis. The difference between the shoe and each brace condition was analyzed by repeated-measures ANOVA. The primary outcome was knee flexion at initial contact.


With greater than 10° simulated ankle equinus, the primary gait compensation pattern was increased knee flexion at initial contact. A significant degree of knee flexion occurred ranging from 7° to 22°.


Our data suggests that observed knee flexion at initial contact may be a compensation pattern in individuals with >10° ankle equinus. However, in individuals with ≤10° ankle equinus, observed knee flexion may represent a true gait deviation. This has clinical significance in the realm of cerebral palsy for treatment planning to improve gait.

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The authors acknowledge Howard J. Hillstrom, PhD, for statistics and Andy Tse, CO, for brace fabrication.


Conflict of Interest

Lisa C. Drefus, PT, DPT, Jocelyn F. Hafer, BS, MA, and David M. Scher, MD, have declared that they have no conflict of interest.

Human/Animal Rights

All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2008 (5).

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Informed consent was obtained from all patients for being included in the study.

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Correspondence to Lisa C. Drefus PT, DPT.

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Drefus, L.C., Hafer, J.F. & Scher, D.M. Simulated Ankle Equinus Affects Knee Kinematics During Gait. HSS Jrnl 12, 39–43 (2016).

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  • equinus
  • gait
  • knee kinematics
  • cerebral palsy
  • knee flexion
  • gait compensations