Study:

The Evolution of the Longitudinal Arch:

Conflicting Results Found in the Relationship of the Structure of the Arch and Lower Extremity Injuries

By Kaline Mulvihill

Study:

Discuss the evolution of the longitudinal arch in human feet and the anatomical changes that have occurred

Review the anatomy of the foot

Examine several studies that have been performed on runners to determine if there is a correlation between arch height and common running injuries

Analyze the methods and results of studies to determine if there is a correlation

Discuss further research needed

Medial Longitudinal Arch Anatomy:

Longitudinal arch can be split into 3 arches- transverse, lateral, and medial

The medial arch is the one most commonly associated with running injuries

Anatomy Continued…

• The lateral arch includes the calcaneus, cuboid, and the fifth metatarsal.

• The medial arch, which is the highest point of the arch, includes the calcaneus, navicular, cuneiform and first metatarsal.

The human foot is made up of 26 bones, 30 joints and many tendons, muscles and ligaments.

The foot is a complex structure that is a shock absorber and has extreme weight bearing capacity for upright posture and habitual bipedal locomotion unique to humans

The human foot has evolved from a generalized grasping organ to a specialized organ for weight bearing and balance.

Evolution of the Longitudinal Arch:

Foot remains of Ardipithecus ramidus kaddaba

Ardipithecus ramidus kaddaba (Ethiopia):

First foot remains found of bipedal ancestor

Dates back more than 4 million year ago.

The pedal phalanx was preserved, which had a large plantar curvature and features similar to apes and A. afarensis showing more primitive traits.

Australopithecus anamensis (Kenya)

• 4 million years ago

• almost complete tibia was found that shows more similarities with homo than afarensis. (more modern)

Australopithecus afarensis (Hadar, Ethiopia)

3.5 million years ago

Foot bones showed dorsiflexion toes, which is a modern trait and the calcaneus had a wide tuberosity, depicting both primitive and modern traits. The phalanges were still long and were curved, which point to arboreal locomotion

A. afarensis was fully bipedal based on the femur.

Australopithecus africanus (South Africa)

“Littlefoot” was discovered and dated back about 3 million years ago

primitive talus, but a modern non-opposable hallux.

Paranthopus robustus (Ethiopia Kenya)

2.5 million year ago.

The inferior side of the foot was expanded, indicating that there were developed plantar ligaments and most likely a well-developed longitudinal arch.

Homo Habilis (Tanzania, Kenya and South Africa)

1.75 million years ago

non-opposable hallux and medial longitudinal arch, but some primitive, arboreal features were seen.

Homo neanderthalenis

very similar to modern humans.

longitudinal arch was well developed, but was slightly medial compared to modern humans

Homo florensiensis

94,000-13,000 years ago

commonly referred to as the “hobbit” because of the small stature and long feet

As the foot evolved, so did the type of locomotion:

The development of the medial longitudinal arch made it possible and more efficient to run

Humans have become skilled endurance runners

During bipedal locomotion, the foot is the only structure that makes direct contact with the ground and is under extreme pressure from the body weight as well as maintaining balance

While running, the pressure increases and can cause pain or injury

In 2009, over 500,000 people finished a marathon in the United States

Running has evolved from a necessary locomotion to a recreational activity

With this increase of runners, came an increase of running related injuries

Attempt to Classify Arch Types to Understand Injuries:

Several measurements have been used to identify and classify arch heights as neutral, high or low.

Some of these measurements include footprint parameters, anthropometic and radiographic technique

Plantar Fasciitis is the 3rd most common running injury:

In a study by Joao et al., it is stated that the arches are more elevated with those who suffer from plantar fasciitis.

A possible explanation: the elevation of the plantar arch is higher than a normal arch, which would cause more strain on the plantar fascia to maintain arch structure during static position.

According to a study performed by Gallo et al.:

higher arches are correlated with bony related injuries

lower arches are correlated with soft tissue damage

They also said that these risks could be the cause of injuries:

age, gender, weight, knee alignment, flexibility, training, frequency, race, distance, running experience, shoe age, lifestyle, previous injuries, and medical problems

Another risk that many runners ignore is increasing mileage, which increases the risk of injury by over use

A study done on 295 Israeli soldiers found a higher incident of stress fractures among soldiers who had categorized high arches.

The high arched individuals showed more femoral and tibial stress injuries, where low arch individuals have more metatarsal injuries.

The United States Army performed a study on 248 soldiers who were in training

The study showed a ratio of 2:4 for high versus low arches of injuries with lower extremities and the lower back.

Cresswell et al. performed a study to see the importance of the plantar intrinsic foot muscles

found that these muscles were important to the medial side of the foot

Weakness in these muscles could result in plantar fasciitis, hallux valgus, and medial tibial stress syndrome caused by reduced ability to control the foot

According to a study by Lohman et al, six out of ten runners were estimated to get injured each year

Lohman et al. study focused on different running styles to prevent injuries

Traditional shod running, POSE running, CHI running and minimalist running styles are compared

Barefoot running

Evolution of Running Shoes:

Initial heel strike contact in running is a fairly new concept in the last few decades associated with the modern running shoes with thick cushioned heels

The new style of shoes becoming popular are minimalist shoes

Conclusion:

There are between 3-6 million runners in the United States

Common injuries being seen are both bony and soft tissue injuries as well as stress on the ligaments.

There is not a positive correlation between these injuries and the height of the arches, just possibilities of what might be causing the problems

More research needs to be focused on footwear development for runners and research on new styles of running.