Let's suppose a healthy fit barefoot young adult standing comfortably on a flat solid surface.
A reasonable guess is somewhere around the foot. But is it the ankle, the heel, or the Metatarsus?
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1$\begingroup$ ankle seems reasonable. pressure is force/area, but higher you climb, less mass you have to support (neck vs lumbar vertebrae) $\endgroup$– aaaaa says reinstate MonicaJun 24, 2015 at 5:46
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2$\begingroup$ the graph here shows that peak pressure is higher at the Metatarsus compared to the heel. however I cannot find a convincing comparison between ankel and Metatarsus. $\endgroup$– Grigori SunJun 24, 2015 at 6:34
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$\begingroup$ What about the base of the spinal column? Very small surface area compared to the two feet, bearing a huge fraction of the load of the upper body. I'm not sure at all about this one, just speculating. $\endgroup$– CorvusJun 25, 2015 at 4:54
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2 Answers
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It is logically clear that the ankle could only partly be analyzed in the group of joints that are below its height. There is no direct way to measure the pressure on ankle joint (on talus bone), but from the logic it is clear that it should be the point of highest pressure in the group of points lister in the question, however the pressure is distributed through the other joints of the foot.
Below are the graphs of pressure distribution according to surfaces (not joints). From the graph we can conclude that part of the pressure experienced by ankle joint distributed tangentially to metatarsal region and other surfaces.
Indeed the highest pressure in standing person in on feets. The term you are asking about is foot pressure distribution (FPD).
In we assess the FPD dynamically, in younger persons the FPD is nearly equivalent between calcaneus region and metatarsal region, while in older persons the FDT in calcaneus region is higher than metatarsal pressure.
During stance:
Foot pressure distribution. A. Maximum pressure distribution on all sensors during stance for one subject. B. The nine anatomical masks superimposed on the insole (MC = medial calcaneus, LC = lateral calcaneus, MA = medial arch, LA = lateral arch, MT1 = first metatarse, 3 = second and third metatarse, 4 = fourth and fifth metatarse, H = hallux, and T = toes).
Pressure distribution by anatomical region. Normalized maximum pressure distribution for the young (white bar) and elderly (black bar) group for each anatomical region (medial calcalneus mask p = 0.0001, lateral calcaneus mask p = 0.03):
source article, you can find much more using FPD as a keyword.
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1$\begingroup$ Thanks for your answer. It is clear and informaitive. Maybe someone can run a simulator of human foot on computer and get a 3D pressure map? It'll be fantastic. $\endgroup$ Jun 25, 2015 at 9:30
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$\begingroup$ @GrigoriSun I'd say this simulator is a good candidate for PhD for someone... %) $\endgroup$– IlanJun 25, 2015 at 9:41
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Note that estimations in this answer are very very crude. I can speak with confidence that the mean pressure of ankel joint is greater than the heel and the metatarsus. However I do not trust that it can pin down the point with most pressure.
@Ilan gave a very good synopsis on foot pressure distribution. However, pressure in ankles was not analyzed in his answer.
Kimizuka et. al. measured contact area of human ankle joints under various load-force configurations. The main results were shown in the graph below.
For a $70kg$ human, the contact area of each ankle is about $3cm^2$, whereas of each foot with ground surface is approximately $37 cm^2$. Please note that we include only the heel ($4cm\times4cm$) and the metatarsus ($7cm\times 3cm$) in above calculation, which sustain most pressure.
We can safely ignore the mass of both feet compared to the whole body. So it seems that ankle pressure is the clear winner here.