Definition

A foot with an excessively high arch.

Overview

Pes cavus occurs in up to 15% of the population, of which 60% will develop foot pain (Burns 2005). Common complaints associated with pes cavus include pain under the metatarsal heads and the heel, lateral ankle sprains, and footwear issues. Custom orthoses should be designed to address the pathomechanics of problematic cavus foot based on the evidence in the literature.

Clinical Goal for Orthotic Treatment

The orthosis for the treatment of pes cavus foot must accomplish several specific goals:

• Increase plantar surface contact area. The overload on the metatarsal heads is a result of limited plantar surface contact due to the high arch and limited ankle joint dorsiflexion. Increasing plantar surface contact with an orthosis ensures that more of the foot is bearing weight in the arch and the metatarsal heads are bearing less weight for less time.
• Resist excessive supination. Lateral ankle instability and a laterally deviated subtalar joint axis (STJ) are frequently associated with high arched feet. This lateral position of the STJ axis results in excessive supinatory torque around the subtalar joint axis. The prescribed orthosis should be designed to resist this excessive supination.
• Resist both excessive pronation and supination forces. Rearfoot instability is an extension of the laterally deviated subtalar axis. However, in flexible pes cavus feet, midtarsal flexibility complicates the later portion of the stance phase of gait. The forefoot pathology produces midtarsal joint supination that leads to excessive pronation of the rearfoot. Some pes cavus feet suffer from both lateral ankle instability at midstance and rearfoot pronation at late midstance. It is essential that the prescribed orthoses is designed to provide resistance to both excessive pronation and supination forces.

Prescription

To prescribe this device check “Pes Cavus” under the Pathology Specific Orthoses section (Part A) of the prescription form.

Prescription Recommendations

• Polypropylene Shell – semirigid
  • Traditionally, orthoses for patients with cavus feet have been designed to be flexible. However, recent evidence indicates that a more rigid device more effectively transfers force off of painful areas
• Deep Heel Cup
  • A deep heel cup helps control rearfoot instability
• Wide Width
  • A wide orthosis increases the surface area contact with the arch distributing more ground reactive force to the midfoot and away from the forefoot and rearfoot.
• Very Minimum Cast Fill
  • Tight contact with the arch of the foot (total contact orthosis) transfers force off of both the metatarsal heads and heel and onto the mid-arch.
• 0/0 Rearfoot Post with No Lateral Bevel
  • “No lateral bevel” increases the surface contact area and acts to stabilize the orthosis
• EVA Cover to Toes
• Valgus Extension
  • A valgus forefoot extension creates a pronatory moment that counteracts the excessive supinatory moment, resulting in more foot stability
• Heel Lift – 3mm
  • Adding a heel lift to the rearfoot post will plantarflex the talus, allowing some ankle dorsiflextion

Summary

This orthosis is designed to reduce the most common complaints found in those with cavus feet, including metatarsalgia, heel pain, and lateral ankle instability. ProLab clients with further questions about this challenging condition can discuss them with a Medical Consultant.

References

1. Benedetti MG, Catani F, Ceccarelli F, et al. Gait analysis in pes cavus. Gait Posture 5(2):169, 1997.
2. Bennett PJ, Patterson C, Wearing S. et al. Development and validation of a questionnaire designed to measure foot-health status. JAPMA 88(9):419-428, 1998.
3. Brewerton DA, Sandifer PH, Sweetnam DR. “Idiopathic” pes cavus. Br Med J, 2:659-61, 1963.
4. Burns J, Crosbie J, Hunt A, et al. The effect of pes cavus on foot pain and plantar pressure. Clin Biomech, 20(9):877-882, 2005.
5. Burns J, Crosbie J, Ouvrier R, et al.: Effective Orthotic Therapy for the Painful Cavus Foot. JAPMA, 96: 205-211, 2006.
6. Cavanaugh PR, Morag E, Boulton AJ, et al. The relationship of static foot structure to dynamic foot function. J Biomech 30(3):243-50.
7. Chalmers AC, Busby C, Goyert J, et al. Metatarsalgia and rheumatoid arthritis-a randomized, single blind, sequential trial comparing two types of foot orthoses and supportive shoes. J Rheumat 27(7):1643-7, 2000.
8. Crosbie J, Burns J. Are in-shoe pressure characteristics in symptomatic idiopathic pes cavus related to the location of foot pain? Gait Posture 27(1):16-22, 2008.
9. Mueller MJ, Lott DJ, Hastings MK, et al. Efficacy and mechanism of orthotic devices to unload metatarsal heads in people with diabetes and a history of plantar ulcers. Phys Ther 86(6):833-42, 2006.
10. Redmond, A., Burns, J., Crosbie, J., Ouvrier, R., Peat, J.: An initial appraisal of the validity of a criterion based, observational clinical rating system forefoot posture. J Ortho Sports Phys Ther. 31: 160, 2001
11. Redmond AC, Crosbie J, Ouvrier. Development and validation of a novel rating system for scoring standing foot posture: the Foot Posture Index. Clin Biomech 21(1):89-98, 2006.
12. Statler, T.K., Tullis, B.L.: Pes Cavus. JAPMA. 95: 42-52, 2005.
13. Walker M, Fan HJ. Relationship between foot pressure pattern and foot type. Foot Ankle Int 19(6):379-83, 1998.
14. Williams DS, McClay IS, Hammill J. Arch structure and injury patterns in runners. Clin Biomech 16(4):341-47, 2001.
15. Williams DS, McClay IS. Measurements used to characterize the foot and the medial longitudinal arc: reliability and validity. Phys Ther 80(9):864-71, 2000.