A
lthough heel pain occurs with a
variety of injuries (e.g., calcaneal
stress fractures and/or infracalcaneal
bursitis), by far, the most common cause
for heel pain is plantar fasciitis. The
word fascia is Latin for “band,” and the medial
portion of the plantar fascia, which runs from the
medial calcaneal condyle to the base of the hallux,
represents the strongest and most frequently
injured section of the band. Until recently, it was
assumed that excessive lowering of the medial
arch in flat-footed individuals increased tension
in the plantar fascia and overloaded the proximal
insertion of the plantar fascia on the medial
calcaneus. In fact, this increased tensile strain
at this site was believed to be so great that it was
thought to be responsible for the formation of a
calcaneal heel spur.
Although logical, recent research proves that this is not the case, as a
detailed histological study of 22 calcanei with heel spurs reveals the bony
exostosis forms at the origin of abductor digiti minimi and flexor digitorum
brevis, not the plantar fascia (1). This research emphasizes the important
clinical interactions that occur between the plantar fascia and the intrinsic
muscles of the arch: The plantar fascia functions passively to store and
return energy while the intrinsic muscles play a more dynamic role in
variable load sharing, working with the plantar fascia to prevent deflection
of the arch during early stance and assisting with arch elevation during
the latter portion of stance. This explains why the development of plantar
fasciitis is not correlated with arch height and the best kinematic predictor
of the development of plantar fasciitis is the speed in which the digits
dorsiflex during the propulsive period (2).
When flexor digitorum brevis is strong, it effectively decelerates
dorsiflexion of the toes during the propulsive period while equally
distributing pressure between the distal phalanxes and the metatarsal
heads. Weakness of this small but important muscle allows the digits to
dorsiflex rapidly through larger ranges of motion, increasing the tensile
strains placed on the plantar fascia. As a result, successful treatment
requires decelerating the speed of digital dorsiflexion by strengthening
not just the flexor digitorum brevis muscle, but also flexor hallucis longus
and flexor hallucis brevis (Fig. 1). The speed in which the digits dorsiflex
Fig. 1. Flexor digitorum brevis home exercise. The seated
patient places a Thera-Band® beneath the foot, traversing
beneath the lesser toes up to the knee. Tension in the band is
determined by the pulling force at the knee and the patient
actively plantarflexes the toes against resistance (arrow). To
strengthen flexor hallucis longus, this exercise is repeated
beneath the big toe. To improve endurance, 8 sets of 40
repetitions are usually performed daily.
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Current Pedorthics
March/April 2013
15