The midtarsal joint is probably one of the least understood but most important joints of the human foot. During daily weightbearing activities, the midtarsal joint must be compliant enough to allow the foot to adapt to uneven terrain and stiff enough to allow the powerful gastrocnemius and soleus muscles to push the body efficiently forward off the plantar forefoot. The ability of the midtarsal joint to biomechanically optimize the load versus deformation characteristics of the foot is what makes this pedal joint such an important part of the human bipedal locomotor apparatus.
One of the reasons the midtarsal joint has been so poorly understood over the years is because, until recently, there has been little scientific research to shed light on its biomechanical function. In 1941, Manter was the first to describe two simultaneously occurring midtarsal joint “axes,” the oblique transverse tarsal and longitudinal transverse tarsal axes.1 Manter moved non-weightbearing cadaver feet in motion patterns that he believed were the most physiologic.
In 1953, Hicks also studied cadaver feet and found that the oblique and an-terior-posterior midtarsal joint axes were in different locations than Manter’s axes.2 Unfortunately, Manter and Hicks didn’t describe the direction or magnitude of the input force (i.e., external force applied to the foot) that produced their “joint axes.” Knowledge of the input force used is crucial to understanding how these researchers arrived at the location of their midtarsal “axes.”
Then, in 1960, Elftman used his “eye of a connoisseur” method to inspect the joint morphology of the midtarsal joint visually and claimed there was a major and minor “axis of curvature” in both the talonavicular joint and calcaneocuboid joint.3 He proposed that when the major axes of the talonavicular joint and calcaneocuboid joint were parallel to each other with the subtalar joint pronated, there would be more midtarsal joint motion available. Unfortunately, podiatric schools around the world are still teaching this idea that alignment of visually determined midtarsal joint “axes” are what make the midtarsal joint more compliant in pronated feet, even though there is not a shred of research evidence that supports Elftman’s theory.
Thankfully, modern scientific research has provided us with more reliable data to better understand the biomechanical function of the midtarsal joint. In 1983, Van Langelaan implanted metallic beads into 10 cadaver feet with three-dimensional X-ray photogrammetry allowing precise determination of the motions of the talonavicular and calcaneocuboid joints.4 He found that rather than the configuration suggested by Manter and Hicks, both the talonavicular and calcaneocuboid joints had joint axes that constantly moved within space, independent of each other, during pronation and supination of the weightbearing foot.
In more recent research on live patients using 3D motion analysis, Nester and colleagues also refuted the notion that two simultaneously occurring oblique and longitudinal midtarsal joint axes can exist since the same bones can’t be moving in two different directions at the same time and since “axes of rotation do not determine the motion at a joint; rather the motion determines the axis.”5
Additionally, the latest 3D bone pin research in six patients during walking found the talonavicular joint has just as much motion during walking as the ankle joint, and the cuboid-fifth metatarsal joint has more motion than either the calcaneocuboid joint or subtalar joint during walking.6
With these facts in mind, why then is the podiatric profession still teaching this 60-plus-year-old concept when modern biomechanics research has long since disproven these ideas? Likewise, why is the podiatry profession teaching Elftman’s theory — that the alignment of his imaginary talonavicular and calcaneocuboid joint “axes” increase the midtarsal joint range of motion when the subtalar joint is pronated — when there is no research evidence to support it?
It is now time that we, as a profession of foot health specialists, spend more effort keeping current on the latest biomechanical research so we can stop teaching the myths that have long been passed along from one generation of podiatrists to another. This is the best way for us to retain our status as the biomechanics specialists of the foot and ensure that our patients continue to receive the best conservative and surgical care.
Dr. Kirby is an Adjunct Associate Professor within the Department of Applied Biomechanics at the California School of Podiatric Medicine at Samuel Merritt University in Oakland, Calif. He is in private practice in Sacramento, Calif.
- Manter JT. Movements of the subtalar and transverse tarsal joints. Anat Rec. 1981; 80:397-410.
- Hicks JH. The mechanics of the foot. I. The joints. J Anat. 1953; 87(4):25-31.
- Elftman H. The transverse tarsal joint and its control. Clin Orthop. 1960; 16:41-44.
- Van Langelaan EJ. A kinematical analysis of the tarsal joints. Acta Orthop Scand. 1983; 54(Suppl 204):135-229.
- Nester CJ, Findlow A, Bowker P. Scientific approach to the axis of rotation of the midtarsal joint. J Am Podiatr Med Assoc. 2001; 91(2):68-73.
- Lundgren P, Nester C, et al. Invasive in vivo measurement of rear-, mid- and forefoot motion during walking. Gait Posture. 2008; 28(1):93-100.
I find it interesting that Dr. Phillips spends so much time discussing the beliefs of Dr. Merton Root and his interactions with Dr. Root in his comment. My article was about midtarsal joint biomechanics, not about Dr. Root.
Contrary to the beliefs of Dr. Phillips, the research by Chris Nester, PhD and colleagues on midtarsal joint biomechanics is right on the money. It was done on live subjects in a weightbeaing setting. It wasn't done by artificially moving the forefoot on the rearfoot in the patterns that the examiner believes should exist in a non-weightbearing setting since this is what Dr. Root taught him. This is not how modern biomechanics research is performed.
Nester et al described the midtarsal joint using three reference axes to describe the spatial location of the midtarsal joint axis relative to the sagittal, frontal and transverse planes, which is consistent with the modelling of other joint axes within the human body within the international biomechanics community. Modern biomechanics research is not performed by having an examiner moving the forefoot on the rearfoot to create an artificial "two-axis model" that corresponds to the primitive research of authors from over a half century ago. This "two-axis model, which Dr. Phillips still defends, is nothing more than another podiatric myth that is still being perpetuated.
It is hoped that young readers will continue throwing rocks at those who have come before them in an attempt to break down the beliefs that are not based on scientific research and sound biomechanical principles. Hopefully, the young podiatrists of today will not form their opinions solely based on the beliefs of their podiatric teachers whom they admire and praise at the expense of their own objectivity regarding the scientific study of foot and lower extremity function.