Knee pain is one of the most common diseases in sports. It is associated with alterations of knee
kinematics and kinetics as well as muscle activity and thus with a decrease in functional knee
stability. A widely used conservative treatment for knee pain is the use of foot orthoses (FOs). Clear
evidence on knee stability could not yet be provided for foot orthoses. For this reason, the effect of
two different FOs was investigated: prefabricated soft bedding foot orthoses (pFOs) and custom-
made sensorimotor foot orthoses (sFOs). The FOs differed in their structure and their postulated
mechanism of action. Thirty active women with knee pain took part in the study. In order to
investigate the effect of foot orthoses on functional knee stability, single-leg landings were analyzed.
A single-leg landing is shown in the following figure.
In addition, the short-term and long-term effects after twelve weeks of foot orthoses use were
analyzed. As expected, the change in muscle activity differed between the two foot orthoses. The
soft bedding foot orthoses mainly influenced muscle activity during the flight phase of the landing. In
contrast, the sensorimotor foot orthoses mainly influenced muscle activity during the stabilization
phase of the landing from initial ground contact to time to stabilize (TTS). Furthermore, the influence
of muscles acting as knee rotation stabilizers was modified by sensorimotor foot orthoses. The
following figure shows the influence of the semitendinosus muscle on the overall activity of all
investigated muscles for the three measured conditions.
There was an increase in the influence of the semitendinosus when using sensorimotor foot
orthoses.
The soft bedding foot orthoses did not affect knee kinematics and kinetics. In contrast, sensorimotor
foot orthoses reduced the internal rotation of the knee during the stabilization phase of the landing.
Consequently, the results showed different effects of the two investigated foot orthoses on
functional knee stability during single-leg landings. The influence of sensorimotor foot orthoses on
functional knee stability seems to be greater compared to soft bedding foot orthoses. The changes in
muscle activity and the reduction in transversal knee rotation could lead to a reduction in knee load
and, as a consequence, to a reduction in knee pain.
The project was carried out as part of a doctorate in cooperation with Prof. Dr. Heiko Wagner from
the Institute of Sports Science at the WWU Münster.