Pes cavovarus: high arch, first ray plantarflexion, toe clawing, heel varus seen most clearly in rear view
Pes cavus, or ‘hollow foot’, may be defined as an abnormally high longitudinal arch that does not flatten with weight bearing.
In most cavus feet, the key feature is plantar flexion of the forefoot (plantaris), usually most marked in the first ray (hence the forefoot is pronated). The hindfoot is usually in dorsiflexion (calcaneus), although in some neuromuscular conditions the gastrocneumius/soleus complex becomes tight or shortened and the hindfoot comes to lie in equinus. In either case the heel may be neutral, but often lies in varus (cavovarus foot).
In a few feet the predominant feature is severe dorsiflexion deformity of the hindfoot due to gastrocneumius/soleus paralysis. The forefoot comes to lie in a reciprocal plantarflexed position (calcaneocavus foot).
This can cause increased weightbearing for the metatarsal heads and associated metatarsalgia and callus. Clawing of the lesser toes is also a predominant feature.
Cavus is generally thought of as a neurological deformity due to muscle imbalance. Howver, a few people have a clearly non-neurological cause such as trauma, while in others there are no clear neurological signs or family history of neurological disorders such as Charcot-Marie-Tooth disease.