Arch failure and other structures compensating flat feet causing low back and knee pain

Text◆Li Yanxi (physiotherapist)

What exactly are flat feet? What problems can flat feet cause? Does it have to be treated?

(Hong Kong News) The arch of the foot has a complex structure and is supported by many bones and tissues. The arch of the foot has two main functions – absorbing shock and assisting with walking propulsion. Flat feet cause the arch of the foot to lose its function and require other tissue structures to compensate, which can cause fatigue and pain in the arch of the foot, legs, knee joints, hip joints, and even the lumbar spine.

Excessive contact between the sole of the foot and the ground

Flat feet (pes planus) are characterized by partial or complete collapse of the medial longitudinal arch of the foot, causing excessive contact between the sole and the ground under weight-bearing conditions. Flat feet can be divided into two types – functional flat feet and structural flat feet.

Functional flat feet means that when the foot does not bear weight, the arch of the foot appears arched, but when the foot bears weight, the arch disappears and becomes flat. It is caused by acquired factors such as muscle imbalance and strain.

Structural flat feet means that the arch of the foot is flat regardless of whether the foot bears weight or not. It is usually caused by congenital factors such as ligament laxity and bone adhesion.

Do flat feet have to be treated? Before answering this question, you must first understand the composition and function of the foot arch.

supported by different bone tissues

The arch of the foot is composed of the medial longitudinal arch, the lateral longitudinal arch and the transverse arch (Figure b), and is supported by many different bones and tissues. Taking the medial longitudinal arch as an example, it consists of the calcaneus, talus, navicular bone, 3 cuneiform bones, and 3 medial metatarsals. The support of the medial longitudinal arch can be divided into static support and dynamic support.

In terms of static support, the plantar fascia, plantar tendon ligament,

The long and short plantar ligaments are the three most important ligaments that support the arch of the foot.

Among them, the plantar fascia contributes the most, accounting for about 80%.

In terms of dynamic support,

The intrinsic and extrinsic muscles of the foot provide dynamic support to the arch;

The tibialis posterior is considered the most important muscle in stabilizing the arch of the foot when bearing weight.

The arch of the foot has two main functions – to absorb shock and to provide a stiff lever for more efficient transmission of force during walking propulsion. In the early stage of the gait cycle (from initial landing to mid-striation phase, Figure c), the tibia will rotate inward and the subtalar joint will evert, causing the midtarsal joint to unlock and the cuneiform bone to unlock. and the navicular bone become more balanced, making the forefoot a highly mobile bone structure to adapt to the terrain, and also help absorb and disperse part of the reaction force, reducing the stress on the lower limb joints.

During this period, the tibialis posterior muscle is stretched like a spring, using eccentric contraction to control the collapse of the longitudinal arch of the foot to achieve a shock-absorbing and cushioning effect.

It doesn’t affect your life and you don’t need to seek medical treatment.

As the center of body weight moves forward to the foot (mid-to-end stance phase), the tibia rotates externally and the subtalar joint inverts, causing the mid-tarsal joint to lock and the cuneiform and navicular bones to become more vertical. This midtarsal locking mechanism makes the medial longitudinal arch a stable lever, allowing for more effective power transfer during walking propulsion.

Flat feet cause the arch to lose function, causing other structures to compensate. Overcompensation may cause different problems, ranging from arch pain, leg fatigue and foot deformities to severe pain in the knee, hip and lumbar spine due to compensation. If you have the above pain it is recommended to seek professional advice and find suitable help. However, even if you have flat feet, the above problems may not occur. If it does not affect your life, there is no need to seek medical treatment.

Increase support and reduce stress Physical therapy to improve flat feet

Physical therapy improves the problem of flat feet by strengthening support for the arches and reducing pressure on the arches.

◆Strengthen support

1. Strengthen muscles

Exercise therapy strengthens individual muscles to increase arch support. The tibialis posterior muscle is one of the most important muscles in supporting the arch of the foot. Failure of the tibialis posterior muscle often causes the arch of the foot to lose support and become flat. In addition, the flexor digitorum longus muscle is also very important in supporting the arch of the foot. Therefore, we can train these two groups of muscles to achieve the effect of strengthening the arch of the foot. Do 10 to 12 times as 1 set, repeat 3 sets.

The following are 3 strengthening exercises: (Figure d)

2. Orthopedic insoles

In addition to exercise therapy, insoles can also be used to enhance arch support. The podiatry orthotist will tailor-made insoles based on the patient’s arch to support the arch and reduce the compensation of other structures, thereby relieving pain and improving the function of the arch.

◆Reduce stress

1.Relieve calf pressure

The calf connects to the heel, and if the calf is overly tight, the traction exerted on the heel will put increased pressure on the midfoot, causing the arch to flatten over time. Excessive tightness in the calves can also limit the range of motion of the foot and ankle joints, causing the feet to turn excessively inward when walking, which may worsen flat feet. Therefore, it is very important to relax the calf muscles to reduce the load on the arch of the foot. (Figure e)

2. Relax the plantar fascia

Heel and arch pain caused by flat feet is usually caused by tightness in the plantar fascia, which becomes tight by overcompensating for flat arches. Therefore, relaxing the plantar fascia can effectively relieve the discomfort of flat feet. (Figure f)

(The above information is for reference only. If you feel any discomfort during exercise, stop immediately and consult a physical therapist)

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