Orthotic device effect on muscles could ease patellofemoral pain

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From Biomechanics Magazine March 2005

Orthotic device effect on muscles could ease patellofemoral pain

By: R.

Foot orthoses have long been used by practitioners to improve their

patients' alignment and alter the mechanical relationship of involved

joints, but researchers at the University of Virginia in

Charlottesville have found that these devices also enhance the

activation of specific lower extremity muscles and may play a role in

the effective rehabilitation of patients with patellofemoral pain.

Jay Hertel, PhD, ATC, an assistant professor of kinesiology, Brent R.

Sloss, ATC, of the Georgia Southern University in Statesboro, and

E. Earl, PhD, ATC, an assistant professor of human movement

sciences at the University of Wisconsin - Milwaukee measured surface

electromyographic activity in 30 healthy young adult volunteers

during specific tasks with four interventions: no orthosis, an

orthosis with a 7 degrees medial rearfoot post, an orthosis with a 4

degrees lateral rearfoot post, and an orthosis with a neutral

rearfoot post.

Ten each of 30 volunteers had one of the following foot types: pes

planus, pes cavus, and pes rectus (neutral). Maximal voluntary

isometric contraction was measured for three muscles (vastus

medialis, vastus lateralis, and gluteus medius) during three

exercises (single-leg squat, lateral step-down, and maximum vertical

jump). All devices were off-the-shelf.

The results showed that in all subjects, activity in the vastus

medialis and gluteus medius muscles was greater while wearing each of

the orthotic devices. Muscle activity was also greater than the no-

orthosis condition while wearing each of the orthotic devices,

regardless of foot type. Again regardless of foot type, in all

subjects there was less activity of the vastus lateralis in the

vertical jump when wearing any of the devices than when wearing no

device.

The results showed that during slow and controlled tasks, such as the

single-leg squat or lateral step-down exercises, the activity of the

vastus medialis and gluteus medius muscles is enhanced with orthotic

intervention, Hertel said.

The findings may help practitioners improve rehabilitation protocols

for patients with patellofemoral pain, he said.

" Orthoses may be useful early in the treatment of patellofemoral pain

when clinicians often want to increase the recruitment of the vastus

medialis and gluteus medius, " Hertel said.

He noted that the results did not carry over to so-called explosive

tasks, in this case the vertical jump exercise. In fact, the

researchers found less vastus lateralis activity during the vertical

jump with any of the orthoses and foot types.

" Interestingly, our results did not show differences in muscle

activation for this exercise among subjects with different foot

postures or with the different orthotic device postings, " Hertel

said.

The fact that foot type or device type did not influence muscle

activation, Hertel said, may have implications for how practitioners

think about the role of orthoses.

" All of the orthoses, regardless of posting direction, were

associated with increased activation of the vastus medialis and

gluteus medius except during the explosive tasks, " he said. " This

suggests that the neuromuscular benefits of foot orthoses may be due

not to changes in skeletal alignment, but rather to enhanced

stimulation of the cutaneous sensory receptors on the sole of the

foot. "

Hertel said the next step in their research is to repeat this study

in patients who have patellofemoral pain syndrome.

The study was first presented in part at the National Athletic

Trainers Association annual meeting in June 2002 in Dallas and was

published in the January issue of Archives of Physical Medicine and

Rehabilitation.