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Monday 8:30am - 5pm Tuesday 8:30am - 5pm Wednesday 8:30am - 5pm Thursday 8:30am - 5pm Friday 8:30am - 5pm

Kevin A. Kirby, DPM, 5120 Manzanita Avenue, #100, Carmichael, CA (2025)

Dr. Kevin Kirby graduated from the California College of Podiatric Medicine in 1983 and completed his first year surgical residency at the Veteran’s Administration Hospital in Palo Alto, California. He spent his second post-graduate year doing the Fellowship in Podiatric Biomechanics at CCPM where he also earned his MS degree. Dr. Kirby has authored or co-authored 27 articles in peer-reviewed journals, has authored or co-authored five book chapters, and has authored five books on foot and lower extremity biomechanics and orthosis therapy, all five of which have been translated into Spanish language editions. He has invented the subtalar joint axis palpation technique, the anterior axial radiographic projection, the supination resistance test, the maximum pronation test and the medial heel skive and lateral heel skive orthosis techniques. He has also created and developed the Subtalar Joint Axis Location and Rotational Equilibrium Theory of Foot Function and has co-developed the Subtalar Joint Equilibrium and Tissue Stress Approach to Biomechanical Therapy of the Foot and Lower Extremity. He has lectured internationally on 33 separate occasions in China, Spain, Belgium, New Zealand, Australia, England, Dominican Republic and Canada over the past 23 years on foot and lower extremity biomechanics, foot orthoses, and sports medicine. He has also lectured extensively throughout the United States. Dr. Kirby is a member of the editorial advisory board for the Journal of the American Podiatric Medical Association and a manuscript reviewer for the Journal of Biomechanics, Journal of Foot and Ankle Surgery, Medicine and Science in Sport and Exercise, Journal of Foot and Ankle Research and Journal of Sports Sciences. He is currently an Adjunct Associate Professor in the Department of Applied Biomechanics at the California School of Podiatric Medicine and has a full time podiatric biomechanics and surgical practice in Sacramento, California.

08/18/2025

Study Demonstrates Importance of Plantar Fascia and Windlass in Maintaining Stiffness of Longitudinal Arch of Foot

Finite Element Analysis of Plantar Fascia During Walking: A Quasi-static Simulation

Yen-Nien Chen, MSc, Chih-Wei Chang, MD, MSc, Chun-Ting Li, MSc, Chih-Han Chang, PhD, and Cheng-Feng Lin, PT, PhD

Abstract: The plantar fascia is a primary arch supporting structure of the foot and is often stressed with high tension during ambulation. When the loading on the plantar fascia exceeds its capacity, the inflammatory reaction known as plantar fasciitis may occur. Mechanical overload has been identified as the primary causative factor of plantar fasciitis. However, a knowledge gap exists between how the internal mechanical responses of the plantar fascia react to simple daily activities. Therefore, this study investigated the biomechanical responses of the plantar fascia during loaded stance phase by use of the finite element (FE) modeling.

Methods: A 3-dimensional (3-D) FE foot model comprising bones, cartilage, ligaments, and a complex-shaped plantar fascia was constructed. During the stance phase, the kinematics of the foot movement was reproduced and Achilles tendon force was applied to the insertion site on the calcaneus. All the calculations were made on a single healthy subject.

Results: The results indicated that the plantar fascia underwent peak tension at preswing (83.3% of the stance phase) at approximately 493 N (0.7 body weight). Stress concentrated near the medial calcaneal tubercle. The peak von Mises stress of the fascia increased 2.3 times between the midstance and preswing. The fascia tension increased 66% because of the windlass mechanism.

Conclusion: Because of the membrane element used in the ligament tissue, this FE model was able to simulate the mechanical structure of the foot. After prescribing kinematics of the distal tibia, the proposed model indicated the internal fascia was stressed in response to the loaded stance phase.

Clinical Relevance: Based on the findings of this study, adjustment of gait pattern to reduce heel rise and Achilles tendon force may lower the fascia loading and may further reduce pain in patients with plantar fasciitis.

(Chen YN, Chang CW, Li CT, Chang CH, Lin CF. Finite element analysis of plantar fascia during walking: a quasi-static simulation. Foot & ankle international. 2015 Jan;36(1):90-97.)

https://journals.sagepub.com/.../10.1177/1071100714549189

08/04/2025

Wooden Model Demonstration of Longitudinal Arch Load-Sharing System of Foot

The plantar fascia and plantar ligaments form part of the Longitudinal Arch Load-Sharing System (LALSS) of the Foot which I first described 8 years ago (Kirby KA: Longitudinal arch load-sharing system of the foot. Revista Española de Podología, 28(2), 2017).

My article may be read here:

https://www.sciencedirect.com/.../pii/S0210123817300087

In the wooden model shown here, which I constructed for a seminar workshop on longitudinal arch function about 15 years ago, the mechanical load-sharing functions of the plantar fascia and plantar ligaments are shown. In the human foot, there are four layers of tension load-bearing elements which help maintain, stabilize and help increase the stiffness of the longitudinal arch against weightbearing forces.

Most superficially is the plantar fascia, which sends five strands distally to the bases of each of the proximal phalanges of the digits (the plantar fascia is shown in this wooden model to only connect to the metatarsal heads to make the wooden model more simple).
The remaining elements of the LALSS are, from superficial to deep, the plantar intrinsic muscles, the deep flexor muscles (i.e. posterior tibial, flexor digitorum longus and flexor hallucis longus) and peroneus longus muscles, and the plantar ligaments. Each of these tension load-bearing elements which make up the LALSS work together to maintain longitudinal arch stability during gait and other weightbearing activities.

In my demonstration in the video, the plantar fascia and plantar ligaments are shown as passive tension load-bearing elements which develop greater tension forces within their structures as the vertical load increases on the forefoot which, in turn, causes an increased tendency for the longitudinal arch to flatten. If the plantar fascia is cut or ruptured, the plantar ligaments will have increased load on them due to their load-sharing function. If the plantar ligaments are cut or ruptured, the plantar fascia will have increased load.

Combined with the active functions of the plantar intrinsic muscles and deep flexor and peroneus longus muscles that are controlled by the central nervous system, these four layers of tension load-bearing elements of the longitudinal arch of the human foot provide the longitudinal arch stability and stiffness which is necessary for the bipedal human to perform the weightbearing tasks that are necessary throughout their lifetimes.

https://www.facebook.com/watch/?v=1569619320043727

07/28/2025

International Seminars

Over the past 34 years, it has been my incredible opportunity to be invited to lecture at a total of 52 podiatry and biomechanics seminars in 13 different countries. My wife and I have traveled together on most of these international lecture trips and have become close friends with many international podiatrists and their families over this time. We have always greatly enjoyed our "lecture-vacations" since we have been able to see many beautiful and interesting sights, got to meet some amazing people and have enjoyed experiencing the different foods and cultures of our world. We are looking forward to many more "lecture-vacations" in the coming years.

07/26/2025

This is a posting from today's PM News, which is a daily e-mail blast going to over 22,000 podiatrists in the USA. Congratulations to Bruno Gallart and colleagues for organizing such a wonderful podiatry conference for the podiatrists of Brazil.

Address

5120 Manzanita Avenue, #100
Carmichael, CA
95608

Opening Hours

Monday	8:30am - 5pm
Tuesday	8:30am - 5pm
Wednesday	8:30am - 5pm
Thursday	8:30am - 5pm
Friday	8:30am - 5pm

Telephone

+19169258111

Website

http://www.kirbypodiatry.com/

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