Subtle cavus foot: diagnosis and management.

The subtle cavovarus foot (SCF) is a mild malalignment caused by either primary hindfoot varus or a plantarflexed first ray, resulting in a typical constellation of symptoms because of altered foot mechanics. Key clinical signs are a peek-a-boo heel and a positive Coleman block test. The cavovarus position places lateral ankle soft-tissue structures, such as the anterior talofibular ligament and the peroneal tendons, on stretch during normal gait. This can lead to common conditions such as lateral ankle instability, peroneal tendon tears, and stress fractures of the lateral metatarsals and cuboid. The gait cycle is altered because a greater proportion of time is spent with the transverse tarsal joints locked due to the overall varus foot position. In contradistinction to physiologic valgus at heel strike, which maintains the transverse tarsal joints unlocked and affords approximately 50% force dissipation, the increased rigidity of the foot causes a maldistribution of forces that leads to accelerated wear of the midfoot joints and increased stresses along the plantar fascia and the Achilles tendon insertion. Successful nonsurgical management requires correction of the biomechanical anomaly; surgical management of a subtle cavovarus foot typically is part of a comprehensive plan for correcting the symptoms and the malalignment.