Investigating First Metatarsophalangeal Joint Dorsiflexion Resistance in Plantar Fasciopathy
Study by: Gabriel Moisan, Dominic Chicoine, Sean McBride, Pier-Luc Isabelle, Álvaro Gómez-Carrión, Nader Farahpour
Plantar fasciopathy is one of the most common musculoskeletal foot disorders, affecting millions worldwide. Traditionally, it has been linked to a dysfunctional windlass mechanism, which plays a key role in arch support during movement. However, recent research challenges this assumption by exploring first metatarsophalangeal joint (1st MPJ) dorsiflexion resistance in individuals with and without plantar fasciopathy.
The Windlass Mechanism and Plantar Fasciopathy
The windlass mechanism is a fundamental biomechanical process in foot function. It involves the tightening of the plantar fascia when the 1st MPJ dorsiflexes, which raises the arch and stabilizes the foot. Previous theories suggested that plantar fasciopathy might result from a failure of this mechanism, leading to excessive strain and heel pain. However, until now, no study had quantified the relationship between 1st MPJ dorsiflexion resistance and plantar fasciopathy.
Study Overview: Measuring 1st MPJ Dorsiflexion Resistance
Researchers conducted a case-control study comparing 20 individuals with plantar fasciopathy and 20 healthy controls. Using a hand-held dynamometer, they measured the force required to dorsiflex the 1st MPJ and activate the windlass mechanism.
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Hypothesis: Individuals with plantar fasciopathy would exhibit greater 1st MPJ dorsiflexion resistance due to a dysfunctional windlass mechanism.
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Methodology: Each participant’s dorsiflexion resistance was compared between injured and non-injured feet and correlated with two orthopedic tests: the Supination Resistance Test (SRT) and the Foot Posture Index (FPI).
Key Findings: Is the Windlass Mechanism at Fault?
Contrary to expectations, the study found no significant differences in 1st MPJ dorsiflexion resistance between:
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Injured and healthy feet in the plantar fasciopathy group.
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Plantar fasciopathy patients and healthy controls.
These findings suggest that a dysfunctional windlass mechanism may not be a primary factor in plantar fasciopathy, prompting a reassessment of current biomechanical models.
Strong Correlation with Supination Resistance
One of the study’s most intriguing results was the moderate to strong correlation (r = 0.674 to 0.891) between 1st MPJ dorsiflexion resistance and supination resistance in both groups. This means that:
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Feet with higher supination resistance also required more force to dorsiflex the 1st MPJ.
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The Supination Resistance Test may be a better predictor of foot biomechanics than previously thought.
Weak Correlation with Foot Posture Index
In contrast, the study found no significant correlation between 1st MPJ dorsiflexion resistance and the Foot Posture Index (FPI). This suggests that foot posture alone is not a strong indicator of 1st MPJ dorsiflexion stiffness, further challenging traditional assessment methods.
Clinical Implications: Rethinking Plantar Fasciopathy Treatment
These results suggest that plantar fasciopathy treatment should focus on other biomechanical factors rather than solely targeting the windlass mechanism. Clinicians may need to:
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Consider foot muscle strengthening instead of only addressing arch stiffness.
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Use the Supination Resistance Test alongside other assessments for a more accurate evaluation.
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Reassess orthotic prescriptions, focusing on individualized approaches rather than relying on outdated biomechanical models.
Conclusion: A Shift in Foot Biomechanics Research
This study provides strong evidence that plantar fasciopathy is not necessarily linked to 1st MPJ dorsiflexion resistance. Instead, the relationship between supination resistance and foot function deserves further investigation. Future research should explore alternative explanations for plantar fasciopathy and refine treatment strategies based on individualized biomechanical assessments.
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