The arches of the foot are architectural wonders that provide stability, shock absorption, and weight distribution. Comprising three primary arches - the medial longitudinal, lateral longitudinal, and transverse arches - these structures play a crucial role in maintaining balance and facilitating efficient locomotion. In this article, we explore the intricate design and biomechanics of the foot arches, their significance in foot health, and common conditions affecting these structures. Join us as we unravel the secrets behind these remarkable natural supports that allow us to navigate the world on our feet.
Arch mechanics
There are several factors that support and maintain the shape of an arch. These factors are derived from the mechanics of stone masonry. The structures that support the arches of the foot are categorized into these factors. Therefore, understanding the arch mechanics will help you understand the role of each muscle, ligament, tendon, and bone in maintaining the shape of the arch
1. Shape of the stones
The stones in the arch are shaped so that they fit each other perfectly to form an arch.
The highest point in the arch is known as the Summit and the stone at the highest point is known as the Keystone. Keystone is the stone where forces from both pillars meet, and therefore it handles a higher pressure than the rest of the stones. the stones that are in contact with the ground are known as Pillars. They transmit the weight of the arch onto the ground.
2. Slips / Staples / Inter segmental ties
These are short structures that attach a few adjacent pieces of stone together.
3. Tie beams
Tie beams are longer structures that connect the opposite pillars together. They span across the arch and attach.
4. Suspensions
These are structures that give an upward force on the arch usually closer to the summit. Suspension bridges use this mechanism to structurally support the bridge
All these factors combined, maintain the proper curvature of the arches of the foot as well. The only difference is instead of stones, in the foot there are bones. And instead of wooden or metal supports, there are muscles ligaments and tendons functioning as supports.
Other important terms of arch mechanics :
Summit - The highest point of the arch
Keystone - The stone at the highest point of the arch where forces from both pillars meet.
Transverse Arches
The transverse arch is described as one arch in certain literature and as two separate arches (proximal and distal) in some other literature. In this article, we will discuss both ways.
Posterior Transverse Arch
The posterior transverse arch is the the arch that is described as 'The transverse arch' in certain books. The proximal transverse arch is described as an incomplete arch as only one pillar touches the ground (lateral pillar). The medial pillar rests on the medial longitudinal arch. The bones involved in the posterior transverse arch are
- The proximal heads of metatarsals
- The 3 cuneiform bones
- Cubiod
The peroneus longus acts as a tie beam of the proximal transverse arch, and it is the main stabilizing factor.
Distal Transverse Arch.
The distal transverse arch is formed by the distal heads of the metatarsal bones. Dorsal interossei and transverse head of abductor hallucis forms the intersegmental ties of this arch
Medial Longitudinal Arch
The bones forming the medial longitudinal arch are
- Calcaneus
- Navicular
- 3 Cuneiform bones
- First 3 metatarsals
The heads of the first 3 metatarsals make the anterior pillar of this arch and the medial tubercle of calcaneus makes the posterior pillar. The keystone is the body of talus and the superior surface of the body of talus is the summit. The arch is stabilized by intersegmental ties/slips /staples, tie beams and suspensions which are made of muscles and ligaments. The main stabilizing factor is muscles.
The intersegmental ties are,
- Plantar calcaneonavicular ligament (spring ligament)
- Long plantar ligament
- Short plantar ligament
The tie beams are,
- Plantar aponeurosis
- Flexor digitorum brevis
- Flexor digitorum longus
- Flexor hallucis longus
- Flexor hallucis brevis.
The arch is suspended by,
- Tibialis anterior
- Tibialis posterior
- Deltoid ligament
Lateral Longitudinal Arch
The lateral longitudinal arch is made by the following bones
- Calcaneus
- Cuboid
- Lateral 2 metatarsals
The heads of the 4th and 5th metatarsals form the anterior pillar and the medial tubercle of the calcaneus forms the posterior pillar. The medial longitudinal arch also shares the same posterior pillar. The summit is the superior surface of the calcaneus. The keystone is the cuboid.
In contrast to the medial longitudinal arch, the main stabilizing factor of the lateral longitudinal arch is ligaments. This arch also has many intersegmental ties, tie beams and suspensions.
The Intersegmental ties are,
- Long plantar ligament.
- Short plantar ligament.
- Short muscles of the foot.
Tie beams are,
- Plantar aponeurosis
- Abductor digiti minimi
- Flexor digitorum longus
- Flexor digitorum brevis
The arch is suspended by,
- Peroneus longus
- Peroneus brevis
Functions of the Arches
- Distribute body weight — The main function of the arches is to distribute the bodyweight. The weight of the entire body is spread out into several weight-bearing areas of the soul which are capable of doing so. These weight-bearing areas are the pillars of the arches.
- Act as a spring — This is mainly done by the medial longitudinal arch. When running and walking, this is important to maintain a smooth gait.
- Act as a shock absorber – When jumping, the impact of striking the foot on the ground is absorbed partly by these arches.
- Protect the soft tissues of the foot – The soft tissues of the foot which are not specialized for weight-bearing, are protected because of the arches of the foot.
Clinicals
Pes Planus.
This is a more common deformity which is generally referred to as flat foot.
Pes Cavus.
Pes Cavus is an exaggeration of the arch. It is charaterized by an elevation of the longitudinal arch of the foot.
Arches of the Foot Quiz
This quiz tests some extra knowledge that was not mentioned in the video. Hope you learn from it
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