Inner meniscus damage and „comfortable shoes“

Millions of people in Germany suffer from knee pain. In 2014, approximately four hundred thousand people were operated on for inner meniscus problems, mainly using minimally invasive arthroscopic techniques. Of these operations, over 200 000 were carried out in doctors’ practices and out-patient clinics.

This enormous number of operations represents the highest number to date in a development over decades, starting in the 1980s before the introduction of orthoscopic surgery.

The diagram shows an example of the rapid increase in these medical conditions.

Statistics illustrate the development of the in-patient knee operations carried out between 2000 and 2015. The reduction in cases over the past few years is due to the increase in out-patient operations.

It is particularly noticeable that women are much more frequently operated on than men. If out-patient operations are included in the calculation, the steady increase in operations is alarming.

There is no explanation for this development. In the past few years and particularly since we have been fighting the root cause of knee, hip and back pain with the InGASys, an answer to this question is surfacing which has bio-mechanical origins.

Gonarthrose im Krankenhaus behandelt

Physiologically normal barefoot walking

During each step, when the foot is in contact with the ground, the longitudinal arch assumes a cushioning and leading function in determining the direction of the step. After the lateral heel contacts the ground, the longitudinal arch lowers during the middle standing phase to absorb the shock in the short foot muscles and to save energy. Once the foot muscles have reached their greatest possible expansion, they tense and catapult the foot into the flexing phase. This causes the energetic springy gait with which we are all familiar.

The greatest possible expansion in the short, medial foot muscles is restricted by the activation of pressure sensors in the skin of the longitudinal arch. On touching the longitudinal arch, the tensed foot muscles contract as a reflex and introduce the stepping action.


The natural lowering of the longitudinal arch also protects the knee from dangerous overload. When the longitudinal arch sinks, the front and back shin muscles stretch.
While both these muscles act as supinators, they create a sling around the shin, protecting the knee from varus angulation. The greater the lowering of the longitudinal arch, the greater the medial pull on the shin.

For the pressure on the knee, this means that the energy vector carries out a medial-lateral-medial movement during the „stationary“ phase of the step and therefore does not create any long-term pressure peaks on the meniscus (see figure 1).

According to a study in which several hundred test subjects were accompanied for a day with the InGAsys, results showed a ratio of 5:1 in standing versus stepping phases for a normal, actively working individual.
80% of the load is a standing load.

The short foot muscles in the longitudinal arch also determine the course of the energy vector in the knee during long standing phases. When standing, the muscles stretch until the longitudinal arch flattens out.

When touched, the muscles tense and again raise the longitudinal arch. In this way, the foot muscles are trained during long standing periods and the energy progression in the knee is constantly changing (see figure 2).

The influence of the shape of the foot on the pressure distribution in the knee is minimal. Only pathological shapes such as flat feet or contracted high arches have any negative effect.


External influences

For centuries, human beings have been wearing shoes to protect their feet from injury. In the 1980s, a technological development in shoe manufacture established itself which is used in the majority of shoes produced nowadays.

This is the foam shoe lining made of PUR, EVA or other foam-based synthetic material. These materials can be produced with minimal effort in a variety of consistencies. 

At the same time, there was a group of customers suffering from extreme foot pain.
These were women aged between 40 and 50 who had worn pumps as dictated by the fashion trends of the 60s and 70s and were now suffering from painful splay foot and valgus. 
For this very large group of affluent and keen shoppers, we developed the “comfort shoe”.

This shoe type is equipped with a cushioned sole and additional cushioning under the metatarsal head, to prevent pain in the forefoot. Over the past few years, the „comfort shoe“ has developed into a leading fashion trend, so that nowadays it is difficult to find any normal or sports shoe without a soft or cushioned insole on the market.

Effects of soft soles and cushioned insoles on the knee

Both components of comfortable shoes work by negatively changing the course of the energy vector in the knee. While cushioned insoles affect the flow of energy by slightly raising the longitudinal arch when walking, soft soles have a constant effect. If both components are built into the shoe, they mutually reinforce one another.

Soft soles when walking

Synthetic soles made of PUR or EVA generally have a consistency/stability of around 40 to 50 shore A.
Since the treading energy always placing constant slightly lateral pressure on the heel area of the sole, so much pressure is brought to bear on the material after a short wearing that the internal structure changes, causing the stability in this area to be severely reduced.The foot sinks deeper into the sole on the outside edge and is forced into a constantly supine position.This means that the longitudinal arch can no longer lower itself to stabilize the knee joint via the shin muscle sling.
The deeper the foot sinks into the soft sole, the smaller the area in which the energy vector can vary.

(see figure 3).



Particularly in long standing phases, a fixated energy vector has a destructive effect on the meniscus cartilage tissue. Tears in the meniscus are unavoidable. If a supporting element is integrated under the longitudinal arch, the effect described above is intensified when walking.

If the sensors in the skin of the longitudinal arch make contact with the support before they have lowered, the muscles contract and raise the longitudinal arch prematurely. This causes a change in the direction via the fourth toe and fixates the energy vector in the medial area when walking too. The higher the support is integrated, the smaller the effective range of the knee.  

If you wear a flexible shoe with a soft sole and an insole with a high longitudinal arch support, there will be an increased possibility of developing a tear in the dorsal part of meniscus. Many patients initially feel an improvement in their condition when they start using insoles.

This can be explained by a change in the knee’s active radius. Unfortunately, the fixated pressure has a negative effect even after a short exposure time. This means many of those affected try to relieve the pressure on the painful areas of their knee by changing their shoes often.  

These interdependencies show that the exploding number of operations of the past decades were caused by a global megatrend in the shoe fashion industry. Since the effect of this misalignment does not end at the knee, this can lead to other muscular-skeletal conditions.

It can also help to explain the later development of knee osteoarthrosis, Cox arthrosis and disc prolapse (slipped discs), depending on the length of time that the customer was exposed to the altered energy vector.

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