Pes Cavus is a high arched foot. ‘Pes’ means foot in Latin and ‘Cavus’ means like a cave. The Pes Cavus foot shape is not uncommon – between 10 and 25% of people have this foot shape. I have pes cavus feet and the associated feature of equinus foot, where your forefoot points down relative to your hindfoot, and mildly clawed toes. All of these features go together in the variation of the Pes Cavus foot known as the ‘cavovarus foot’. In the cavovarus foot the hind part of the foot is in varus (leaning outwards). In my case this is just by 5 degrees. This causes the foot to roll less which means that your foot absorbs greater stress on the inner part of the heel on heel strike. This stress is then transmitted up the leg to the knees and other joints. This is why I have injuries to the inner part of both of my knees.
Apparently there is little rigorous scientific data about the cavus foot. Some people can have a cavus foot and be asymptomatic. Mine is ‘idiopathic’ i.e. not associated with any known pathology. It is believed that the cavus foot can be caused by a number of factors, including an imbalance in strength between the muscles operating on the front of the leg (tibialis anterior and peroneus brevis) and the back of the leg (tibialis posterior and peroneus longus), where the front muscles are pulling too tightly. It may also be caused by structural abnormalities in the shape of the bones.