What is the term for a low arch of the foot?

Terminology for Low Arch of the Foot

The medical term for a low arch of the foot is "pes planus," commonly known as flatfoot. 1

Types and Classification

• Flatfoot (pes planus) is characterized by a decreased or collapsed medial longitudinal arch of the foot, resulting in more of the sole making contact with the ground 1, 2
• In contrast, a high arch is known as "pes cavus" 1, 3
• The condition can be assessed using various measurements including arch index (AI), which classifies foot arches into low, normal, and high categories 4

Anatomical Considerations

• The foot has two primary arch structures:
  • The medial longitudinal arch (MLA) - runs along the inner side of the foot 3, 5
  • The transverse tarsal arch (TTA) - runs across the width of the midfoot 3, 5
• In flatfoot, there is typically a collapse of the medial longitudinal arch, but the transverse arch may also be affected 3
• Recent research shows that the transverse arch contributes significantly (over 40%) to the longitudinal stiffness of the foot 5

Clinical Implications

• Contrary to common belief, individuals with flat feet may actually be at lower risk for exercise-related injuries compared to those with high arches 6
• A study of military trainees found that those with the flattest feet had the lowest injury risk, while those with high arches had significantly higher risk (odds ratio of 6.1) 6
• Flat feet can lead to inappropriate foot pressure distribution and potential foot injuries in some cases 2
• Progressive collapsing foot deformity (PCFD) represents a more severe condition where there is progressive loss of stiffness and collapse of the medial longitudinal arch 3

Assessment Methods

• Arch height can be measured through several methods:
  • Ink footprint test to measure arch index 2, 4
  • Weightbearing CT imaging for more detailed assessment 3
  • The transverse arch plantar (TAP) angle - measures the angle formed between the first, second, and fifth metatarsals in the coronal plane 3
• Simplified clinical methods like the arch index diagonals (AId) method have been developed to make assessment more practical in clinical settings 4

Management Considerations

• For symptomatic flat feet, management may include:
  • Appropriate footwear modifications 1
  • Custom-made insoles or orthotic devices 1, 2
  • Artificial arch supports to improve pressure distribution 2
• For patients with foot pain related to arch problems, the American Academy of Family Physicians recommends:
  • Appropriate orthotic modifications
  • Open-backed shoes
  • NSAIDs for pain management
  • Activity modification
  • Stretching exercises 1

Clinical Pearls

• When evaluating patients with flat feet, it's important to distinguish between flexible and rigid flatfoot, as management approaches differ 1
• Artificial arch supports have been shown to effectively improve excessive peak pressure and poor body stability in patients with flat feet 2
• The location of arch collapse in progressive collapsing foot deformity is most significant at the second metatarsal and medial cuneiform 3