The Arches of the Foot
The figure below shows the medial longitudinal, lateral longitudinal, and transverse arches of the foot. The talus, cuboid, and intermediate cuneiform bones function as keystones to these arches. These bones have joint surfaces that form a wedge to provide support. Interlocking joint surfaces also provide support.

Although skeletal structure is important to arch support, without the ligaments, the arches would collapse. The plantar ligaments (ligaments on the bottom of the foot), which are stronger and larger than dorsal ligaments (ligaments on top of the foot), tie the inferior edges of the bones together. The most important ligament in the maintenance of the medial longitudinal arch is the plantar calcaneonavicular, or spring ligament.(1,2)

 

Insertion on the calcaneus and navicular bones allows this ligament to function like a tie beam in an arch. The long and short plantar ligaments provide the main support for the lateral longitudinal arch. The deep transverse ligaments support the transverse arch.
 

It turns out that the ligaments are the most important soft tissue supports for the foot and the arches. A study to determine the role of muscle activity in arch support found that men standing on one foot could support loads of 200 pounds without any evidence of muscular activity as measured by electromyography.3 These findings suggest that the primary mechanism of arch support is ligamentous and that muscle activity provides support only when loads become excessive.

When an athlete has pain on the bottom of the foot or foot fatigue, it is typically because one of these ligaments is weakened. If a positive jump sign is elicited when the spring ligaments, deep transverse ligaments, or plantar ligaments are palpated, then Prolotherapy is performed to these structures. Prolotherapy is extremely effective at stimulating the growth of these ligaments, which aids in their ability to support the arch.

There is another sports medicine myth we must discuss here. A myth that is commonly perpetuated is that flat feet are bad. At one point, low-arched individuals were banned from service in the U.S. Army.4 A collaborative study of 248 Army trainees recently examined the risk factors associated with training-related lower extremity injuries. Foot morphology data were collected from the new recruits before basic training. The recruits with the lowest injury rates had the lowest arch heights. High-arched individuals had the highest training-related foot injuries.5 This makes sense because the ligaments would have more strain placed on them in high-arched individuals. It is actually the high-arched individuals who need arch supports, not the flat-footed athletes. We will commonly prescribe arch supports, in addition to Prolotherapy, for those with pain in the arch who have especially high arches.

1. Snell, R. Clinical Anatomy for Medical Students. Second Edition. Little, Brown and Company, Boston. pp. 543-570.
2. Foot morphology. NIKE Sports Research Review, Beaverton, OR, August/November 1990.
3. Basmajian, J. Journal of Bone and Joint Surgery. 1963; 31B:1184-1190.
4. Foot morphology. NIKE Sports Research Review, Beaverton, OR, August/November 1990.
5. Cowan, D. Med. Sci. Sports and Exerc. 1989; S60:2.