Short- and long-term influences of a custom foot orthotic intervention on lower extremity dynamics
Christopher L MacLean1, Irene S Davis, Joseph Hamill
1Biomechanics Laboratory, Department of Kinesiology, University of Massachusetts-Amherst, Amherst, Massachusetts, USA. cmaclean@parisorthotics.com
Objective:
The objective of the current study was to analyze the influence of a short-term and long-term custom foot orthotic (CFO) intervention on the lower extremity dynamics in a group of female runners with a history of overuse running knee injury.
Design:
Descriptive laboratory study.
Setting:
University of Massachusetts Biomechanics Laboratory, Amherst, MA.
Participants:
This study included a group of female recreational runners (15 to 40 km per week) who had a history of overuse running knee injury in the 6 months leading up to the study.
Intervention:
Semi-rigid, custom foot orthoses manufactured from a neutral suspension cast and designed to meet the specific needs of each subject. Subjects wore the custom foot orthoses during all running activities for a period of 6 weeks.
Main Outcome Measures:
Three-dimensional ankle and knee dynamics were collected while subjects performed over-ground running trials with and without a CFO intervention. Data were collected before and after a 6-week CFO intervention during all running activities.
Results:
For ankle parameters, short-term intervention led to significant decreases in maximum values for rearfoot eversion angle and velocity, impact peak, and loading rate. Ankle inversion impulse was also significantly decreased during the loading phase. At the knee, maximum knee external rotation moment was significantly increased when subjects wore the custom foot orthoses.
Conclusions:
The 6-week intervention led to subjective changes, including a significant decrease in pain. An improvement in symptoms did occur with the 6-week intervention. In addition, dynamic results revealed that custom foot orthoses have an immediate effect on dynamics and that this influence occurs only when orthoses are worn in the footwear. The short-term CFO intervention led to significant decreases in rearfoot kinematics (maximum eversion angle and velocity) but no changes observed in knee kinematics. The kinetic analysis revealed that these subjects exhibited significant decreases in maxima for ankle inversion moment and angular impulse during the loading phase, impact peak, and vertical loading rate with short-term, CFO intervention. At the knee, the CFO condition led to increases in knee external rotation moment maxima and angular impulse.
