With the verticalization of posture beginning at age 2 years, humans become sole walkers, putting first weight first on the heel of the leading foot and then rolling onto the ball of this foot, while pushing down- and backwards with the toe and forefoot flexors of the non-weight-bearing opposite limb (upright gait of the Pharaoh and the nomads). The adoption of the usual cultural footwear, school enrollment, the practicing and promotion of forefoot weight-bearing by habitual “head-before-heel” walking, the heels of shoes, rolling onto the ball of the forefoot and reduced toe movements due to tight shoes, as well as standing and sitting with weight-bearing on the forefoot have resulted in habitual overloading of the passive plantar fascia close to its origin by prolonged-traction and impulse-related mechanical trauma and of the metatarsal bones by repetitive bending strain (stress fractures) (1).
The distribution of body weight on the plantar surface causes the tracks of the runner, and not the other way around. In persons with normal motor function, the distribution of the body weight over the time integral is the primary determinant of the loading and development of the foot, still before foot motor function.
Habitual inclination posture, highest loading on the forefoot and reduced toe motor function, especially of the long flexor muscles, lead to shortening of the calf, achillodynia and overloading of the plantar fascia and the metatarsal bone, which can be described as a chain syndrome (2). The weakest link develops symptoms, while “protecting” the other chain links. The load is spontaneously taken off the painful side; consequently, the load increases on the opposite side, which may then start to hurt.
Using ultrasound, measurements of the cross-section of the plantar fascia close to its origin can be obtained bilaterally for comparison and over the course of treatment to determine the acuteness and painfulness of the plantar insertional tendonitis (3). The bony heel spur represents the repair of the insertional tendonitis; the site at risk of rupture is covered by calcified material. This biomechanical functional considerations allow for causal treatment strategies with proven effectiveness in affected patients (3).
Footnotes
Conflict of interest
The author declares no conflict of interest.
References
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