Pes cavus, cavovarus, or high-arch foot are all descriptive terms used to describe a foot in which the arch is higher than typical population norms. It is the opposite of pes planus, or flatfoot, in which the foot has little or no arch. Sometimes a cavus foot, just like a flatfoot, can be problematic. However, the problems seen with cavus feet are generally different, and in some ways, opposite of the problems seen with flat feet.
Severely cavus feet may not fit into shoes very well because of their shape. They can seemingly toe-in when walking. They may appear to have a humpback deformity with 'bossing' on top of the foot that can become painful from shoe pressure where the laces tie across the foot.
A cavus foot is less flexible than a flatfoot. For this reason, during walking, cavus feet do not absorb shock as well. Due to this stiffness and rigidity, a cavus foot is more prone to arthritic changes in the midfoot and hindfoot. These arthritic changes may cause the bone to remodel and grow spurs (osteophytes), which can exacerbate the painful pressure and bossing on top of the foot. The arthritic changes may also cause achiness in the arch and the midfoot after a long day of standing or walking. This lack of flexibility and shock absorption may also predispose to other foot conditions such as plantar fasciitis related heel pain (see section on plantar fasciitis).
Patients with cavus feet can also present with symptoms of lateral ankle instability (see section on ankle sprains). Ankle instability is a diagnosis in which patients have recurrent ankle sprains, or the feeling that their ankle is unstable or will give way. The causes of ankle instability are variable but may be influenced by foot shape. Patients with cavus feet tend to walk on the outer border of the sole (lateral column) or the side of the foot. Based on laws of physics, walking on the outside of the foot puts tension on the lateral soft tissue restraints and renders these individuals more prone to 'rolling' the ankle, and experience an ankle sprain. Severe ankle sprains can lead to permanent damage of the lateral ligaments and tendons, which leads to even more sprains or further instability. This can become a cycle leading to increased sprain frequency and increased ankle damage such as anterior talofibular ligament (ATFL) tears, peroneal tendon tears, and cartilage damage (osteochondral defects).
Even in patients with cavus feet who don’t experience severe sprains or instability, the peroneal tendons (see section on peroneal tendons), which serve to stabilize the ankle, may become overworked or injured. As the patient walks on the outer sole of the foot, the peroneal tendons work to stabilize the foot and keep it from rolling in and preventing sprains. This can lead to soreness, tendonitis, or painful spasm of the tendons and sometimes peroneal tendon tears. Often times, in order to successfully repair peroneal tendon damage, the cavus shape of the foot must be addressed simultaneously.